I'd stay in Montrose or Vevey. I went in the spring and it was lovely. Second the train up the mountain there. I see you've dropped Berne, but it has the best chocolate in the world. Tschirren. It's a small store near the train station. There are several streets with covered side walks (with arches to the street). The store is on the first or second street from the river (on the river side). I didn't see the brand anywhere else in Switzerland, but it may be.