The Saver Pass is valid for areas shown on the GA Map. You do NOT need a GA card to purchase a Saver Pass.
If you have a ½ Fare Card, Saver Passes are cheaper.
One suggestion, traveling from Zurich to Luzerm and using the Golden Pass routing from Luzern to Interlaken Ost (departs Luzern at XX:05 for most of the day) has super scenery on this section.