we have stayed in that area twice now, at two different b&b 's. I would highly recommend a b&b instead of a hotel, as you will get local advice on what to see and do. especially with a car, as you can move around so easily.
last year we had a farm stay near ramsau ( a few miles outside berchtesgaden) , it was a great change, as the owners were so helpful and on their recommendations we did things that we would not have thought of. it really made the holiday.
eating out in berchtesgaden is easy, there are a number of options. parking in town is easy, there is an underground car parking station in the main town. its not expensive to park.
we would just drive into town each night and park, then eat and wander around, its a nice town to just wander around and look at the painted buildings. driving around the whole area is very easy, the traffic is good.
one 'different' option is to visit the local therme, for a swim in the different pools ( they are open til late) we did it one night and met so locals, it was something different to experience.
hope this helps.