Suggestions on our itinerary

First, I would advise you to mark how many nights you spend in each place, rather than days. It gives you a more accurate idea of the amount of time you have. For example, you have 3 days listed in Dresden, but really, if you are getting there on the 7th and then leaving on the 10th to go to Nuremberg, that only gives you 2 full days (3 nights) there, since the day getting there and the day leaving will both be tied up a lot with driving.

That said, it's probably enough time for Dresden. It might be a bit tight when you get to Nuremberg, as it looks like you are arriving in Nuremberg on the 10th day and then leaving on the 12th. This gives you two nights in Nuremberg, but really it's only one full day, so either Rothenburg or Nuremburg will probably suffer a bit. I mean, you can always see part of Nuremberg on the day you get there, but I would imagine that you would be leaving early on the 12th, so that really only gives you maybe a day and some change.

And again, you've got 5 days for the Rhine and Moselle valleys, but really, if you're staying there from the 17th and leaving on the 21st, that only gives you 4 nights and therefore 3 full days there. That's certainly enough for that area, I think, but it's easier to be realistic if you are realistic with your dates.

Also, your itinerary is a little confusing. Are you taking the train to Berlin right after you land in Frankfurt? And just out of curiosity, why aren't you flying into Berlin? You could fly into Berlin and out of Frankfurt using a multi-city option when you book. I would strongly suggest considering that option. It's usually not much more expensive, and when you factor in the time involved in taking the train from Frankfurt to Berlin and the cost, you're probably looking at at least, at the very least, breaking even but possibly even saving money.

One other thought. Depending on where you're staying on the Rhine, Heidelberg is actually close enough that you could potentially do it as a day trip, which would save you from having to spend one night in a place and then moving on. That always adds time that could be better spent sightseeing.

Not rushed

Good selection of destinations for history museums and a good pace imo.

Rental car for Nuremberg and Munich makes no sense. Use widely trains and public transport. I would earliest rent one when leaving Munich. For rental car you will likely need IDP (regulation).

You will miss the Northern part of Germany with own history, e. g. Vikings, Hanseatic League, own impressive architecture style Brick Gothic, and some interesting WWII sights such as submarines. I will not recommend to change plan because you have to prioritize and spend time at destinations.

A few comments:

-- I wouldn't rent the car until you reach Nürnberg. The train between the two is just about as fast, and if you're not planning on making stops midway, why make life harder for yourself? Public transit between Nürnberg and Rothenburg is possible but involves multiple transfers, though, so the car would be helpful to have by that point.

-- If you're visiting Tübingen and want to see some other nice small towns nearby, you could do a loop Herrenberg-Calw-Weil der Stadt-Magstadt-Tübingen. Or, for a more scenic drive from Tübingen to Heidelberg, you could do Tübingen-Herrenberg-Calw-Bad Libenzel-Pforzheim, and pick up your original route. Or stop by Speyer on the way between Karlsruhe and Heidelberg, which is definitely worth a visit.

(Edited to add: Pforzheim is not scenic and not worth a stop! I only include it to give you an indication of the driving route.)

"As history enthusiasts, we prefer a slower pace with a focus on culture, museums, and exploring offbeat paths."

Your pacing is doable.

Aside from the one day for Tübingen, I feel under-informed on your personal interests and intentions in the country. "History" and "culture" can mean almost anything. Cultures of all kinds have been tromping across Germany for many centuries. What kinds of museums? "Offbeat paths" might indeed contribute a bit of adventure, but they are absent from your plans, which pretty much follow the pre-approved, Rick-Steves-penned, "well-beaten path" that the other summertime tourists will be taking through Germany:

https://www.ricksteves.com/europe/germany/itinerary

"...your suggestions will help us make our itinerary better without feeling too rushed."

With your relaxed pace in mind, new ideas would likely need to REPLACE parts of your current itinerary. We will need to better understand your travel interests as well as which of your planned stops can be dropped - and which are "must-keep."

Your very 1st day is too rushed! Flying into Frankfurt and then taking a 4 hour train to Berlin means you arrive completely exhausted. Stay the night in Frankfurt, walk around in the sunshine and get some sightseeing done, go to bed early and catch a morning train to Berlin. You will feel so much better and enjoy your time here.
There is certainly enough here to see on both your first and last days here. Historically and culturally.

Thank you all for your helpful replies. Below is a more detailed version of our itinerary. Please note that this is still a work in progress. :-)

Berlin

• Day 1: Arrive in Frankfurt; take a flight or train to Berlin. Aim to arrive by evening and stay overnight in Berlin.
• Days 2–5: Explore Berlin. Sleep in Berlin.
• Day 6: Check out and store luggage in a locker. Spend the full day in Berlin before taking a late evening train to Dresden. Sleep in Dresden. (Total: 5 full days in Berlin)

Dresden

• Days 7–8: Explore Dresden. Sleep in Dresden.
• Day 9: Check out and store luggage in a locker. Spend the full day in Dresden, pick up a rental car, and drive to Nuremberg. Sleep in Nuremberg. (Total: 3 full days in Dresden)

Nuremberg & Rothenburg

• Day 10: Full day in Nuremberg. Sleep in Nuremberg.
• Day 11: Check out early and drive to Rothenburg. Full day in Rothenburg. Sleep in Rothenburg.

Munich & Day Trips

• Day 12: Check out and drive the Romantic Road to Munich, including a stop in Dinkelsbühl. Explore Munich in evening and stay there overnight
• Day 13: Day trip to Dachau and potentially Augsburg. Explore Munich in evening and stay overnight.
• Day 14: Check out early. Drive to Neuschwanstein Castle, then proceed to Tübingen after dinner. Sleep in Tübingen.

Tübingen Detour

• Day 15: Check out and explore Tübingen and near around places. Drive to Bacharach. Sleep in Bacharach.

Rhine/Moselle Valley & Heidelberg

• Days 16–18: Explore the Rhine Valley. Sleep in Bacharach.
• Day 19: Check out and spend the day in the Moselle Valley. Sleep in Zell.
• Day 20: Explore the Moselle Valley. Sleep in Zell.

• Day 21: Check out and spend the full day in Trier. Drive to Frankfurt to return the rental car (or return the car in Trier and take the train). Sleep in Frankfurt.

• Day 22: Fly out of Frankfurt. (All good things come to an end!)

Our thoughts behind some of the questions :
- Not covering Rhine valley in start - We considered starting with the Rhine and Moselle valleys, but decided against driving immediately upon arrival due to potential jet lag.
- Why to rent a car before Munich - Flexibility. Also, we plan to have a car to follow the Romantic road from Rothenburg to Munich as this route was highly recommended.
- Our Interests - We are looking forward to exploring German history, spanning from Roman times through German unification and beyond. We realize three weeks only scratches the surface, but we want to cover as much as possible at an enjoyable pace.
- To keep a slower pace, we decided to skip Northwest Germany for this trip but plan to include it in a future visit to the Netherlands and Belgium.

Thank you so much again!

How "flexible" is the new work-in-progress version with details? I understand that you are traveling mid-May and are probably not eager to re-do things. But here's my feedback nonetheless. I'll just focus on the first part of your trip here.

• Train to Berlin from FRA on Day 1: still a bad idea. You're looking at 4.5 hours or more on 2-3 different trains. You cannot predict flight arrival times, wait times for security and baggage, etc., so you can't grab one of those "saver-fare" tickets (which are non-refundable if you fail to travel as scheduled) as there's no good way to predict what time you can reach the train station... the walk-up fares will be very high, possibly in the neighborhood of €150 each.

If I were writing this itinerary, the Rhine and Mosel Rivers would come first since they are so close to FRA airport. After you clear baggage, I would of course avoid driving - jetlag looms, as you mentioned - so here's what I'd do...

Day 1)...head to the airport station and take a local train to Bacharach (or another Rhine town.) See the town that day. Relax. Take a late afternoon Rhine Cruise? That shouldn't tax you too much. This train trip costs only €16, no matter when you buy it, and there are departures around the clock, including some DIRECT regional express trains that take less than one hour. Just get your ticket at the airport station whenever you are ready and catch the next train.

Day 2)... "explore the Rhine" first by catching a local train to Koblenz. This is Germany's most scenic train ride. Pick up your car at Hertz there - it's right at the station. Then go about the rest of your plans for the Rhine and Mosel.

There are two medieval castles in the area you should check out. The really medieval-looking one is Marksburg in Braubach. Then there's Burg Eltz.

https://www.marksburg.de/en/
https://delveintoeurope.com/braubach-germany/

https://burg-eltz.de/en/homepage

You can travel north on the Rhine to Remagen to see the WW II "Bridge at Remagen" museum (see the movie before going.)

https://www.tripadvisor.com/Attraction_Review-g642105-d2165317-Reviews-Peace_Museum_Bridge_at_Remagen-Remagen_Rhineland_Palatinate.html

Bacharach does not have any hotels with river-view rooms. I always advise visitors who want that option to book in St Goar (Hotel Rheinfels or Rheinhotel St Goar have GREAT views across the water and are right next to the K-D boat dock and fery crossing.)

https://dynamic-media-cdn.tripadvisor.com/media/photo-o/18/9e/0f/df/rheinhotel-st-goar.jpg?w=1400&h=-1&s=1

Boppard has even more riverfront hotels and restaurants on its nicely-developed waterfront. A nice wine garden too. Nice chairlift ride there too. And all guests there receive a free Guest card good for free train travel and other discounts:

https://www.boppard-tourismus.de/media/was-ist-wo-broschu__re_en_190219.pdf
https://www.staedte-fotos.de/1200/rheinufer-promenade-boppard-23082016--65743.jpg
https://www.boppard-tourismus.de/en/accommodation/
https://www.deutschlandgourmet.info/bilder/gross/5710-Restaurant-Weinhaus-Heilig-Grab-Boppard.jpg

After the Rhine Mosel, turn in your car at Koblenz and catch the train there for Berlin. This time, you can arrange to CATCH your train, so a saver-fare ticket would be the way to go.

Additional comments:

1) Bacharach is a beautiful town. It's only 10 minutes from St Goar and a few more from Boppard, so if you stay in one of these other towns, do make the drive to see Bacharach.

2) Braubach (home of Marksburg) is also pretty stunning. Take a walk through town while there.

3) For history/museum fans, SPEYER offers an amazing tangle of it for a town of its size. An outstanding Romanesque cathedral, Jewish history, and the country's most incredible tech-museum. I would recommend staying there instead of your 1 night in Heidelberg.

https://www.tripadvisor.com/Attractions-g198634-Activities-oa0-Speyer_Rhineland_Palatinate.html

4) I'd take the train from Dresden to Nuremberg (saver fare) and rent the car when leaving Nuremberg. You will not need any flexibility for the Dresden > Nuremberg drive since it's an evening drive and you won't have time for sightseing.

5) Please look into the historic towns of Bamberg and Erfurt before choosing to head straight to Nuremberg. Both of these two towns are right on the train route to Nuremberg and are tops when it comes to old-world charm and history; both are UNESCO World Heritage sites as well. They are worth your time.

Bamberg: https://i.pinimg.com/originals/bc/4d/c1/bc4dc191b3a25c5d084fd1e60e5aea84.jpg
Erfurt: https://www.tripadvisor.com/Attractions-g187419-Activities-oa0-Erfurt_Thuringia.html

6) Very nice outdoor cultural musem in Franconia (where Nuremberg and Rothenburg are located)... stop there on the way to Rothenburg?

https://www.tripadvisor.com/Attraction_Review-g198421-d284746-Reviews-Frankonian_Open_Air_Museum-Bad_Windsheim_Middle_Franconia_Franconia_Bavaria.html

FYI you may not have to pay to leave your bags at the station-- a lot of hotels will store your bags in a secure room until you come to pick them up again, if you ask.

Surprisingly, I'm the first to say: take the Night Watchman Tour in Rothenburg.

Since it seems that Roman history is your thing, then other places come to mind: Trier, Cologne, Mainz, or the Saalburg Roman fort near Frankfurt.

Thank you for your suggestions and advice on our itinerary. After weighing our options, we have fine-tuned our plans. We decided to reduce our stay in the Rhine/Moselle valley by one day and add that time to Nuremberg to better explore the city and Regensburg. Additionally, instead of driving from Dresden to Nuremberg, we will now take the train and rent a car once we arrive in Nuremberg.

---- NEED HELP ON THIS
We have also begun making reservations and have a question regarding our stay in Dresden. While we booked Airbnbs in Berlin, Dresden, Nuremberg, and Sankt Goar, only our Dresden host has asked us to fill out an arrival form on hostaway.com. They mentioned this is a requirement under the German Registration Act and requires personal information such as dates of birth.

Since we are entering Germany through Frankfurt, I assumed all necessary immigration formalities would be completed there. We did not encounter similar requests during our previous trip to Scandinavia, and our other German hosts have not asked for this information.

Could you please let me know if it is standard practice or necessary to fill out this form?

Thank you so much once again!

Never had to go on that website myself just to book a room. Sounds like the kind of information that hotels typically get from you upon check-in. Not sure why they want all that in advance.

Collecting detailed data from guests ahead of time is often done when there will be no host present at check-in, or when there is no convenient on-site means to make copies of the key pages of passports.