You may be a bit confuses on what a “ticket” gives you. A ticket is just a proof you paid for transportation. A pass replaces a ticket. So you do not need to get another ticket (or pass) for pretty much any train in Switzerland. The pass is your ticket. All you do is find your train and get on, and on the train you show your pass when the conductor comes.
Reservations are completely separate, live in their own universe. On some trains you must have a reservation. On other trains you can, but on most trains there are no reservations. All you need is a ticket, or a pass.
If you have an Eurail Flex Pass then just do not activate it on the day you bought the Saver Day Pass for, as the Saver Day pass gives you unlimited travel on all public transit in Switzerland.