what pass I should get

They have not made a perfect-fit Swiss Travel Pass for the number of days that you could be using one in this plan. You have to choose between 8 consecutive days for about $435, 8 flexi days within a month at $485, or "overpaying" (but getting the fullest coverage) for 15 consecutive days at $530.

All benefits for which you decide to use the pass do start use of a flexipass travel day, whether fully covered or just discounted. Mountain lifts can get expensive, so plan to use a pass for those. If any of your days in a city like Luzern or Montreux involve only in-city transport, then your hotel will probably give you city card to cover those.

You also have the option to buy a one-month Half-Fare Card, which will certainly be cheaper than paying full fare everywhere. But I have not done the math to add up ticket prices for all your possible trip elements (listed or not listed). That's the time investment you would make if you really want to calculate what's cheapest. However, you may do that math and still come up with more than one option at a similar total.