DeniGroz Hello,
If you want discounted tickets, it is better to buy them in advance, but note that you must take the trains mentioned on the ticket.
Such tickets are partially or not exchangeable and partially or not refundable. It is valid for Austria, Switzerland and France.
The Saver Day Passes are valid only in Switzerland, but you are too late for Fri, 03.05.2024, they are now expensive.
The easier solution is to buy direct tickets from Salzburg to Geneva, saver tickets are available.
Another solution could be to buy separate tickets for Austria (Salzburg - Buchs SG with a group discount) and for Switzerland (Buchs SG - Geneva with Supersaver Tickets).
Sorry, I cannot say what solution is cheaper.