Seat reservations are not a thing in Switzerland: they are available on some trains but nobody makes them except few tourists (lived here all my life and never made one).
The country works like a giant subway system. People hop on, hop off and sit wherever they want. Trains are long and capacity is plenty. If a carriage is busy, simply walk to the next one. Don't overthink it. :)
Zermatt-Visp is a regional train. Since Zermatt is a termini station people will board from the rear. Go to the front carriages.
Visp-Lausanne will be empty when you board. It gradually fills up along the way.
Lausanne-Paris TGV high-speed trains indeed have mandatory reservations (29€). France has a lot of mandatory seat reservations (due to infrequent trains/different passenger mentality).
Some info here: https://www.seat61.com/interrail-and-eurail-reservations.htm
France has a lot of mandatory seat reservations (due to infrequent trains/different passenger mentality).
And a very different railway mentality...
Hello @Alan1871
I have often observed that most people wait in the middle of the platform, but more free seats are available at the front or the rear of the trains. You can see on the platform displays how long the train is, where first and second class cars are situated and sometimes an estimated occupancy. The same informations are also available in the SBB Mobile app. Sectors with letters help you to wait in the right place.