Thank you sla019 for the reality check. We had checked the German Alpine Road before and it recommended 4 days. So we checked the Grossglockner being shorter and the altitude, and just got carried away.
Now we’re back to the Deutsche Alpenstrasse.
It seems we have these alternatives:
1- Detour for the Alpine Road between G-P and Lake Chiemsee (crossing Tolzer, Tegernsee and Schliersee) and then just follow the Autobahn etc towards Berchtesgaden.
2- Take road 472 roughly to Lake Chiemsee and then detour for the Alpenstrasse (crossing Chiemsee Alps and Chiemgau region) towards Berchtesgaden.
So maybe we should detour to the Alpine Road either on our way from Ettal to Lake Chiemsee or the portion from Lake Chiemsee to Berchtesgaden in order to be able to take breaks, explore, and enjoy the scenery.
Does that seem doable in a day? Which one would you recommend?