Hello Globtour2024
The number and weight of luggage is not limited. You can take on board what you need for your trip; no dangerous goods or other articles than what you need for travel can be brought on board the public transport vehicles. And, it must not block entry / service doors, aisles, or emergency equipment.
Furthermore, you are responsible yourself for your luggage and must be able to on- and offload it yourself. There are no baggage trolleys available in the stations. My personal advice: travel light-weight, it will ease changing trains. Use laundry services in our country instead.
More information on luggage transportation is given here:
https://www.sbb.ch/en/help-and-contact/products-services/additional-services/other-sbb-services/luggage.html#anchor2
Best wishes,
Roland