How long to spend in Dinkelsbuhl and Nordlingen?

The other year I spent the whole day in Dinkelsbuhl, but I walk in and out of every side street and around the outside and a bit further, including a leisurely lunch. Same with Nordlingen many years earlier. If you are driving, start with Nordlingen, get to the town nice and early for a breakfast of coffee with a ham and cheese kaiser roll, then do a walkabout. Onto Dinkelsbuhl, arrive early afternoon for lunch then do a walkabout. There aren't that many tourist shops in Dinkelsbuhl but the street and houses are very attractive.

Glad you recognize how nice the Romantic Road can be.
Not sure that I would spend 3/4 nights in Rothenburg. You can see the city in one full day. I would plan on one full day for Dinkelsbuhl and Nordlingen together.

If you're driving why not stay the last night in Dinklesbuhl? I will be cheaper and save backtracking to RodT.

I appreciate comments about how long we should or should not spend in Rothenburg, but our time there is accounted for and all I am really concerned with is how many hours we should allot for Dinkelsbuhl and Nordlingen. For instance, if a "full day" means 6 hours between the two towns would cover it, then we'll plan to head onward to Heidelberg that afternoon/evening. But if people think 10 hours is needed for it to be fulfilling and not rushed, for example, then we don't want to then tack on the drive to Heidelberg in the dark after a long day. We can't eat meals out so we either want to be back at our Air BnB in Rothenburg by dinner time, or in our new place in Heidelberg by dinner time. From what I've heard though, I think we're leaning toward heading to Heidelberg that night. I appreciate insights though if that doesn't sound doable. Thanks!

You allowed your planning to revolve around an apartment rental. Next time, I suggest you be more flexible, do your research prior to booking.

I think you will need a full day and that would not give you enough time to leave Rothenburg in the morning after breakfast, see the two towns you mentioned and then drive to Heidelberg in time for dinner (unless you drive in the dark). This is early March, not the Summer.

Enjoy the Romantic Road.

Why do people always jump to being so quick to judge? I haven't booked my lodging yet--that's the point. I'm trying to figure out whether to make that last night be in Rothenburg or Heidelberg. It must be nice to be able to travel and switch hotels without having to worry about planning around where there are kitchens and what time supermarkets close and the time it takes to go grocery shopping and cook something new when you switch to a new city, but I unfortunately do not have that luxury. All I was looking for was time estimates about how long it takes to see the two cities, goodness. So thank you to the parts of the responses that actually addressed my initial question. I think we can consider the thread closed at this point.

I think 6 hours is more than enough

Perhaps you could share your interests, then people could make better suggestions about how long you should stay somewhere? I like old churches and can spend a good bit of time in one. Others are done in 5 min. I also like half timbered buildings, and little museums that small towns have and I really like visiting old cemeteries. I also like taking lots of photos of the above in my attempt to be a better photographer. What do you like?

Also, no one knows why you can't eat out, so calling people out like they know this somehow, is a tiny bit odd.

What we have here is a failure to communicate.

I don't mean to offend, but could have done better in providing important information.

I provide information based on my experience in visiting all these places in the past. I lived in Germany for four years and travel extensively. However, I realize that what I think is the way to do things is not always what others would do.

I have done Rothenburg and the entire Romantic Road twice and the southern end more than that. If you want to stay in one location and do day trips, I understand, I have done that several times. Yes, you will waste some time in travel, but won't have to change lodging as much.
If you have already see Rothenburg, why are you staying there 4 nights?

I suggest that you can do Dinkelsbuhl and Nordlingen in one day, probably in six hours (not counting a meal).

https://www.romanticroadgermany.com

North to South Distance between towns
Würzburg

Tauberbischofsheim 38km
Lauda-Königshofen 10km
Bad Mergentheim 11km
Creglingen 25km
Rothenburg ob der Tauber 19km
Dinkelsbühl 45km
Nördlingen 32km
Harburg 17km
Donauwörth 12km
Augsburg 44km
Landsberg am Lech 39km
Schongau 29km
Pfaffenwinkel (Rottenbuch) 17km
Schwangau 29km
Füssen 4km

We stayed in Dinkelsbühl and it was so charming. That said, a half a day is enough to look around. We enjoyed walking the path around the walls and getting outside the walls for glimpses of the gardens outside. My dad was fascinated by seeing the beautiful gardens in peoples back yards. We enjoyed shopping in the little shops there too.

In Nördlingen we were there about a half days as well. We climbed to the top of the church, and went to the Meteor Museum. It is in German, but they have an English hand out that explains everything. You can also walk the walls there, but we didn't do that.

The two towns are 30 km apart from one another. So I think a day for both makes sense, but it depends on what you want to see.

I would recommend spending more than 6 hours total for both Dinkelsbuhl and Nordlingen; assuming you like to wander the side streets to get an in-depth look at the town. I think you can see one in the morning and then the afternoon (plus supper) in the other before heading back to your hotel.

For you drive to Heidelberg, I would recommend picking up B37 where it crosses the A6 just north of Heilbronn. It's a longer drive but the scenery along the Neckar River can be stunning.