Thanks Carrie (and others),
I have enclosed our general itinerary and other thoughts and questions.
Plan is to arrive Zurich, train to Luzern the same day. Stay in Luzern 3 nights (do boat, Rigi, maybe Pilatus, Glacier Garden, Transport Museum.
Then to Montreux 3 nights; Chillon Castle, boat, train to Gruyeres (castle), Gstaad, possibly Geneva or Zermatt day trips.
Then Golden Epoch (not visiting Gstaad again) to Wilderswil near Interlaken and Grindelwald for a total of 7 nights between the two spots with a lot of travel and exploration in the BO. Likely go to Schilthorn and Jungfraujoch also.
We wondered if we could purchase a Swiss travel pass for the first part of the trip, (prior to visiting the BO area) and while that pass is in effect, buy a BO pass at a discount (the swiss travel pass gives the same discount on the BO pass as the 1/2 fare card) before the swiss travel pass expires.
OR, do both passes need to be valid concurrently to get the BO pass at a discount?
Considering how much travel we plan in both the BO area and outside of it, we are considering a Swiss travel pass for the entire 15 days AND ALSO the BO pass (at a discount) for the time we are in the BO. Even though the Swiss travel Pass would be unused in the BO, we still need to return to Zurich area and the airport, and the Swiss pass would have given us the better rate on the BO pass.
Costly, yes, but having the freedom of travel throughout and the ease of not buying tickets along the way might be worth it (?!).