How long did you spend in Berchtesgaden?
First time (2014): 1 day. Did a Panorama tour from Salzburg that hit Eagle's Nest, salt mine, and Königssee. It was super rushed, but a good introduction to the area. I don't think I would recommend it, but it did convince me I wanted to come back to the area for a longer visit.
Second time (2017): 5 days 🙂. Nature, nature, and more nature (including hiking at Königssee as below).
Third time (2022): 2 days. I went back to Salzburg with a friend who had not been there -- we spent 5 nights in Salzburg and took two full-day day trips to Berchtesgaden. One was for Königssee (caught the boat across the lake -- walked to Obersee [a smaller super picturesque lake], hiked along the right side of Obersee, ascended to an alpine meadow, hiked on to Röthbach Waterfall [the highest waterfall in Germany], visited St Bartholomä). The second day we caught the bus to the salt mine, did the salt mine tour, took the short walk along the river to the bus station, caught the bus out to Eagle's Nest, visited Eagle's Nest, and then returned.