I look at your game plans and like all of those places. But my heart hurts a little for the passing over of rural/alpine/smaller places, places that are so core to the region's identity. For that reason, unless you are the type who relentlessly thrives off museums and fancy buildings, I like the option that incorporates the Salzkammergut in place of 2 nights in Salzburg. Stand on top of a mountain and eat some killer cheeses. Maybe stay in St. Wolfgang and day trip to Hallstatt so you aren't so far out there on your travel-transition days (unless you have a car). Day trip to Salzburg from the Salzkammergut, or hit it up as a stopover on your way to Munich.
The Bavarian castles are impressive! Also, and particularly Neuschwanstein, they are more than willing to consume close to the entirety of a day of your too few days in the region - long lines, hassles to access, waiting for tours, etc. If you do the castles edumacate yourself on the travel-ninga ways of making them efficient. Or else spend your limited time standing around with the rest of the herd of tourists. If you stay our there, I'd say that you might try a place smaller and less touristy than Fussen and then drive in to the castles as you pass through back toward Munich.- the Alps are literally right there, no reason not to be properly in them. Again if you rent a car possibilities open up considerably but it can be done by train.
I love both Munich and Vienna. Munich, I think, yields better to a shorter visit if that's a choice you come up against. One the other hand, Munich is a special city in the sense that it's extremely livable, so if you prefer riding a rental bike to leisurely afternoon at a beer garden on a river bank in a romantic park that's your town. If you are more into cathedral catacombs and visiting a gorgeous opera house, Vienna's your jam. Personally, on my trip this summer I've got 2 nights in Munich at the end, longer stays in some other cities earlier on.
have fun, exciting stuff!
