Berlin, Munich, Rhine area Itinerary

With your arrival and departure days, it looks like 6 days out of 11 that you're actually in transit, on trains, or sitting in train stations. I'd cut Berlin, fly into Munich and start there. The Rhine is where the riesling is made, beer in the other places. Take the train all the wy to Bacharach (via Mainz) and do your river cruise from there. Just my opinion.

Slow down and savor each spot more. It takes so much time to check out of a hotel, travel, check back in. In my opinion, you're traveling too much. We LOVE Saltzberg - I'd add time to that. We also didn't care for Frankfort compared to other amazing towns. If you have time, a day trip to Dachau concentration camp from Munich is well worth it. We used a company from the RS Germany book. It was with Radius Tours. We also did a Day trip to Regensburg with them. We love the smaller, quaint towns more than the large, metropolitan cities - although I think everyone should see Berlin. The Old town of Munich is nice. Nurnberg is another favorite.

I think you should plan for 10 nights, with a final night at your fly-out airport or nearby.

I absolutely agree with dropping Berlin.

Should we reverse this itinerary?

Doing the Rhine FIRST makes for a short train journey after your flight. Fly into FRANKFURT, and you are only about an hour from the Rhine. Either that, or Fly into Munich and later out of FRA.

"...stay in Bacharach or another town on cruise route for 2-3 nights."

Yes to 2-3 nights. But you will find St. Goar to the north to be more central for outings. In part that's because St. Goar has a ferry boat for crossing the river at any hour - which you want to do if you hope to visit the Best Rhine Castle - Marksburg - and visit Ruedesheim (well known wine town.) Boppard is just to the north and Bacharach to the south. Rheinfels Castle is right in town. St. Goar has river-view rooms (not so in Bacharach) as well and is on the most scenic part of the Rhine. And those in the know will tell you that boarding the cruise from Bacharach will cheat you out of half the best scenery. With St. Goar as one end of the cruise, it will be easier.

I think you need at least one night in Salzburg. A day trip from Munich is not enough.

I agree 100% with spending a couple nights in Nuremburg - a good substitute for Berlin (not that it's Berlin.)

nights:
Munich 3
Salzburg 2
Nuremberg 2
St. Goar 2
Mainz (near FRA) or FRA 1

If you can possibly be on the Rhine on April 30 you can catch a unique local festival in Oberwesel - Wine Witch Night. Oberwesel is 5 minutes south of St. Goar by train. There's a parade with torches, a straw wine witch gets burnt at the stake, and a new wine queen gets her crown for the year. Lots of wine too.

https://vlexx-und-los.de/assets/images/3/Oberwesel-Hexennacht_151-41de21f0.jpg

I am of the opposite opinion and would drop Munich for Berlin any day. For me, it is a much more interesting city. So many more things to see and do and there are great cities and towns near-by, like Potsdam, Dresden, Hamburg, Quedlinburg, Lübeck.

If you do make it down to the Rhein area, here are some events in late April that might be of interest:
17-20.04 Spring Fest, Wiesbaden
25.04 Night of the Museums, Frankfurt
30.04 Walpurgis Night, Burg Ronneburg

I don't dislike Berlin, but it takes longer to see than these other places and would mean a much larger travel loop if you intend to do either Salzburg or Munich.

From your original itinerary, I would cut one night from Munich and add to Salzburg ( actually I would add all 3 days to Salzburg ). As I‘m sure Russ mentioned ( I didn‘t read his reply ), do the Rhine boat from Ruedesheim or Bingen to St. Goar or Boppard ( Last time I did Bingen to Boppard)