Looking at 2 or 3 nights in Salzburg then driving to Vienna for 3 nights.
I would be interested in detouring to Braunau am Inn then driving to somewhere like Hallstatt for one night.
The next day driving to Mauthausen to tour and possibly onto Melk touring and staying for one night.
Next day drive onto Vienna and drop off car.
Does this look feasible and not too rushed or should i add an extra night ?
Cheers
Paul