Sep 16, 2016 - 8:44 AM
Hi selina84, welcome to MySwissAlps!
As for the part in Switzerland: personally I would rather stay longer in less towns. There is really not much you can see if you stay for one night only. With two nights you at least have one full day, but no room to be flexible if the weather doesn't allow mountain trips, which I assume you are interested in. Just staying in Lucerne, Montreux and Zermatt would be fine for me.
As for the rail pass: you'd best first have a fixed itinerary, including day trips. I do think either a Swiss Travel Pass or Swiss Half Fare Card will suit your plans, but you need an itinerary to compare them price wise.
The above links provide lots of additional information. Just let us know if you need more help!