Our Rick Steve’s tour ends the morning of Sept.ember 15 and our flight leaves from Munich the evening of September 17. We have 3 days to go from Vienna to Munich. Any suggests?
GAS tour? We went back to Salzburg for a couple of days, (we went to the Marionette theatre, it's amazing), on the train, then train from Salzburg to Munich. It was easy, the only thing I'd do different would be to get a reserved seat from Salzburg to Munich. We wound up standing up the whole way, the train was packed!
IMHO this would be the most efficient use of your short time: Stay in Vienna for one night, on 9/16 take the night train to Munich (dep. 11:25pm, arr. 6:10am), spend the remaining day in Munich before going to the airport.
If you just want to get from Vienna to Munich, the Railjet train is the best way. The most scenic section is between Linz and Salzburg.
If you want to stop off at places along the way, consider Linz, Salzburg, or the Chiemsee.
I just got home from a Munich, Salzburg, Vienna trip and here's what we did. You can do it in reverse.
Munchen to Salzburg using the Bayern Ticket and taking a Meridian train:
Then Salzburg to Wien Westbahnhof using Westbahn: https://westbahn.at/en