I am working my way through planning a 6 week trip, and would appreciate some advice re: train tickets and travel passes. My daughter (18) and I will be traveling from Normandy to Murren in June, and staying for 4 nights. I want to buy the TGV portion of the train trip ASAP since the lower price fares are already less available; but I haven't yet done the research to figure out if we need a Swiss Travel Pass, Berner Overland pass, etc. - and I'm not sure if that will affect my train ticket purchase. If I just buy the ticket from Caen to Paris / Paris to Basel now, is that impacted by any decisions re: Swiss travel passes? is there a downside to buying the train tickets in pieces, rather than all the way through? There seem to be a lot of transfers to get from Basel / Interlaken / Lauterbrunnen / Murren.
Thank you in advance for your help!