In Switzerland reservations are a waste of money. No one makes them except if you want to use the touristic scenic trains with mandatory reservation.
However, on the routes where the scenic trains run, there are also reservation free regional trains which are much better to use.
Will you only be travelling in Switzerland?
You are so helpful, thank you for all of your answers!
Yes, only in Switzerland! And only really to and from Interlaken and Lausanne (with a stop in Grindelwald) to do a few hikes
The Interrail pass includes boat rides on Lake Thun and Brienz. A fantastic experience ! On the other hand it doesn't include travel from Interlaken to Grindelwald or Lauterbrunnen. You get a 25% discount.
Other options :
- Swiss Travel Pass (very expensive) : it covers all public transportation and also gives discounts for mountain peaks (25-50%). Interrail often gives the same discount. There currently is a sale : https://shop.switzerlandtravelcentre.com/?affiliateId=249#/en/product/swissPass
- a combination of Saver Day Passes (from 52 CHF) and regular tickets
- half-fare card (120 CHF) and then half-fare tickets and day passes. Especially worth it if you're going to Jungfraujoch. From Interlaken : 107 CHF (half-fare), 140 CHF (STP), 160 CHF (Interrail), 215 CHF (full-fare)