You can travel from Salzburg to Berchtesgaden either by train via Freilassing (1h05) or by bus (RVO 840, the Watzmann Express, takes 49 minutes). The Watzmann Express makes several stops in Salzburg, one at Mirabell, one across the river from the old town.
A Bayern-Ticket (25€ first person, 6€ each additional person up to 5 total) will cover the train all day (after 9 AM work days).
An RVO TagesTicket (for 10,20€/P) covers the bus all day (the Watzmann Express makes its last run to Salzburg just after 6 pm). Stay later, and you will have to take the train back.
A BGL Tagesticket Bus & Bahn, for 12€/P covers both the trains and buses. There is no 9 AM limit for either.
All three tickets include almost all of the local buses in Berchtesgaden, including RVO 846, which goes to Ramsau by way of Wimmbachbrücke. The Bayern-Ticket does not cover the bus, and the RVO TagesTicket does not cover the trains.
For two people, I would get the BGL TagesTicket Bus & Bahn and take the faster bus to Berchtesgaden, then either the RVO 846 bus to Ramsau or the train to Bad Reichenhall, then the train back to Salzburg.