I'm located 50km south from Munich. I do know about the danube cycleway.
A couple of members of our german language club in england recently cycled from München, but they went to Wien. I hope to have a cycle around the lakes in the Salzburgerland next summer, but just short rides during the day, not touring, as my wife likes to do the tourist thing, coffee and Sachetorte and so on.
We were in Mittenwald and Seefeld last summer. That looks a nice place to ride too, especially the Lautaschtal.