Yes to Tirano, not Torino!
This will be a lovely trip, and good use of a 15-day Swiss Pass ( not Flex as Pat thought). But you are going out of your way in some cases to utilize the named scenic routes, and missing one that should be included.
Take a look at the map of Swiss railways and you can see what I mean:
https://cdn-doc.myswissalps.com/docs/default-source/rail-network-maps/swisstravelpass.pdf?sfvrsn=7788603a_56
First, the Glacier Express: no need to ride all the way to the end at Zermatt, which is a detour on the way to Montreux, if you don’t have a night planned there. It would be a very long day on a train if you go all the way to Montreux by that route.
If you want a good chance to see the Matterhorn, then go to Zermatt and spend 2 nights there (substitute this for the nights at Bern), Then, to reach Montreux, return to Visp from Zermatt, and head to Spiez. There you can board the Golden Pass line and ride that to Montreux, likely with a change at Zweisimmen. This is the “classic” direction to ride the Golden Pass, due to the fantastic views down to Lac Leman as you descend from the mountains to Montreux. And you will have a chance to ride in the special panoramic cars on this section of the route. You can read about them and learn about reservations for the special cars:
https://www.myswissalps.com/goldenpass
https://www.goldenpassline.ch/en/goldenpass-panoramic-2/
Even if the schedule does not work out and you ride a regular regional train, it is a great view and nice way to get to Montreux. Also shorter than the route via Martigney.
After Montreux, you can reverse the route to Spiez and on to Mürren, or go via Bern with or without a stop in the city on the way.
Then from Mürren to Luzern, do not go via Bern. Take the much more scenic route, continuing on the Golden Pass line from Interlaken Ost over the Brunig Pass.
For you last day of using the Swiss Pass, note the comments above on the validity for Rigi versus Pilatus. The Swiss Pass fully cover the Rigi loop, but coverage is only partial for Pilatus.