One more thing: Normal full price tickets are flexible, so for example a full price ticket Interlaken - Munich allows you to take any train on the route within the period of validity of the ticket. (Usually 2 days I believe for such tickets). When you buy a ticket you pay for transport, not for a place on a particular service.
But a discounted ticket will come with restrictions, usually in the form of particular trains you must take. Many tourists expect that to be the case, and are surprised to hear that this is in fact the exception, not the rule.
However if there is a disruption, if one of your trains does not run, or you miss a connection due to a delay your ticket automatically becomes the default standard ticket, so then you can just take any trains you want. And you do not need to do anything for that in Switzerland or Germany. There is no need to exchange tickets or visit the ticket office. Just take the next train...
And a last thing: Reservations are separate, can be bought together with the ticket, and are compulsory for Paris - Base and recommended for Zurich - Munich, but not needed for trains within Switzerland. Do not waste money on that.