On a post about a week ago, a Forum contributor said that a Swiss Travel Pass sale would start April 15.
The SBB app is easy to use. I'd suggest downloading it now, and play with the routes you'll likely be using. The App will give you train #'s, stops, and platform numbers. Platform #'s are important for train transfers. You need to know the platform # you will get off your train, and the platform# of your next connecting train, as often you will have under 10 minutes to make the connection. When your train slows for the station, be at the door with your luggage and be ready to jump off. Obviously, the lighter the luggage the better, and everyone handles their own luggage.
For the scenic routes, note that the regional trains run on the exact same tracks, so you don't have to ride the panoramic trains for the spectacular views . The regional trains require no seat reservation, are much less crowded, are included in the Swiss Travel Pass, and have more schedule options.
The Swiss Travel Pass is so easy to use- no buying tickets, no validation required. The exception is that some of the mountain lifts are not covered, and only discounted. ( Mt Rigi is covered, but Mt Pilatus is a discounted fare.)
Do note that in Switzerland it can get into the 80's in the cities in the summer, but the mountain summits are still quite chilly.
Have a wonderful trip in this beautiful country.