Along the babbling Isar, you can relax (a little) on the softer version of the third day. There are still 800 meters of elevation somewhere along the route, but they are so well distributed that you almost don't notice them.
Easier version of the third stage, which leads on forest and asphalt roads through the Karwendel foothills and along the Sylvensteinsee lake. A leisurely route on which the 800 meters of altitude difference are really pleasantly distributed. Only towards the end does the route tend to climb more.
The slightly easier version of stage 3 leads mainly through the German part of the Karwendel and thus saves a few meters in altitude. You even make a few more downhill meters than uphill meters along the Isar.
Overnight stay in one of the numerous bed & bike accommodations at Lake Achensee or at the Alpen Caravan Park Achensee