Eurail is probably the best option yes. Count how many pass days you might need. I'd go for 7 or 10. 1st class is only a little extra if you feel like it.

Most trains will be included, boats on Lake Thun and Brienz are too. You get a 25% discount on Jungfraujoch but it's still very expensive -> 160 CHF per person. Up to you to decide whether it is worth it or not.

Note the mandatory reservations on Italian fast and high-speed trains (extra costs) : https://www.seat61.com/interrail-and-eurail-reservations.htm

About your itinerary in particular : you're moving around a lot. It doesn't make a lot of sense, especially in Italy. The limited time you have will be mostly spent on trains!

I'd do something like :

- Zurich 1-2 nights

- Interlaken area 2-3 nights

- Rome 3 nights

- Florence 2 nights

- Venice 1 night

- Milan 1 night

The Gotthard Base Tunnel is closed (with little exceptions) so you'll lose 1h each way with the old line. The Lugano - Morcote leg isn't included (bus). Not worth it.

Montreux makes more sense from Interlaken : direct trains, all new and shiny. Go back via Vevey, Lausanne and Bern.

Thank you so much I will look into this itenary again there are Hotel in those places already booked unsure how we going to go about it, really appreciate the suggestion and advice, will discuss with my trip buddies .

Hi sorry one more thing? 2 of us will be flying  out to Zurich from the Uk ( British Passport)  should we purchase interail , and will be returning to Uk from Milan  And the rest of my travelling budies are from Indonesia  ( they would purchase Eurail)  is that correct ? 6 days in Switzerland and 6 days in Italy  I dont know which ticket should we purchase as we can see only 7 day 10 day and 15 days 

Thanks

Yes Interrail for some and Eurail for the others.

Are you flying back to the UK or taking trains? The pass could also be valid from the airport to your hometown (if some of you live far from the airport).

You don't need a pass day if you stay within a city : it's not valid on trams, buses, etc.

I'd probably go with the 10 days pass so you have some margin either way. Up to you!

Yes Some will be flying back to the Uk from Milan