Swiss Travel Pass

No Swiss trains are reserved (except special tourist trains like the Glacier Express or Bernina Express). Hop on, and when the conductor comes by to check tickets, just show your pass.

Cons: it is rather pricey, and depending on your use, not necessarily the lowest price means of travel. If you have more than 240 CHF of full fare tickets planned, 90% of the time, the 30-day Half Fare Card gives the best value at 120 CHF pp. But you still need to purchase tickets for each trip, so the STP has its convenience factor, plus some value at many Swiss museums where it gives free entry. Note, if you get a Flex Pass, free museum admissions are only available on travel days.

For those tourist trains, you need to buy seat reservations, which vary in price by train and season. The STP does cover the actual travel fare.

I haven't been to Switzerland recently and haven't used the Swiss Travel Pass for about 30 years, but I'd be very surprised if it covers any boats offering dinner cruises. I just want to be sure there's no confusion on that point. The STP used to, and I assume still does, cover the lake boats used for basic transportation.

STP also covers local transportation such as city buses and trams, and most museums. I prefer it over the half-fare card for the convenience.

We were in Switzerland last Nov/Dec., and for us the four-day Swiss Travel Pass worked out well. It was great not having to stand in line to buy tickets, or worry about validating tickets. You can maintain a flexible schedule, and just board the train [for example] that arrives when you get to the station.
We also used the Pass in Luzern for the charming boat trip to the Mt. Rigi stop, where the boat is timed [so Swiss!] to meet the cogwheel train to the peak of Mt. Rigi. This was all covered by the Pass. [You do need to do the research, as the cogwheel train to Mt. Pilatus is not covered.]
I don't know about specific dinner cruises, but you can purchase food and drinks on the boats we boarded.
My suggestion is to draft your specific itinerary, being accurate with how much time your activities would take. Then do the math for the days in Switzerland. Do note that the price for specific train trips usually assumes that you have at least the Half-Fare Pass.
Have a great- and healthy- trip!

The other time when you’d have to buy a ticket, in addition to the STP, is when taking a high-mountain ride that’s only discounted many at 50%.

And the most popular mountain train (Jungfraujoch) is only discounted 25%. However, The Half Fare Card will get you a 50% discount.