There was a thread with a question regarding Eurail and/or Swiss Travel pass yesterday so you can start by reading the answers there.

https://community.eurail.com/ask-a-question-40/eurail-global-pass-vs-swiss-travel-pass-8798

Do you want to end up in Berne every night or do you want to make a tour and sleep in different places?

Here you can read about some of the scenic routes. 

 https://www.swissactivities.com/en-ch/travel-guide/travel-tips-switzerland/panoramic-trains-in-switzerland/

Question is which Scenic Lines and mountain rails you wanna ride on? 

Not all Ship Routes and Mountain Rails are covered by Eurail 
Swiss Flexipass cover allmost all Public transport within Switzerland and sometimes a higher discount on Mountain Rails compared to Eurail.

You have to provide more details (which trains, Ships , Mountains you wanna catch) or do the maths on your self :) 

Eurail + Reservation for Paris - Switzerland + not included Rails & Ships (maybe with a discount of 25% -50%) 

Or a Swiss Flexipass + Paris - Bern + Not included mountain rails (some of them with a discount usually 50%) 

Thank you for your responses. 

We are just searching for different options.  Right now we would start from Bern and end up in Zurich.

I am thinking going Zurich to Chur (Bernina Express).  Then Chur to Montreux.  Then Montreux to Zurich.  Taking 3 days to make the trip.

Is that pushing too much in a day?  Are there better cities to stop/stay along that route?

We would buy the second class seats and probably use a boat/ferry in a scenic area (please make a suggestion).  This is all new to us.

Thank you.

This can be all done in one day Maybe long days but it´s possible all these Routes could be done with a Swiss Railpass or with a Eurail Pass Chur - Montreux i recommend to go via Oberalp,Andermatt & Brig to have a nice Journey along the Glacier Express Route
Montreux - Zürich i recommend to go via Zweisimmen - Interlaken Ost - Lucerne to Zürich 

The question is which boat ferry? 
Lake Lucerne (e.g. Lucerne - Vitznau - Mount Rigi - Arth Goldau - Lucerne/Zürich
Lake Lucerne (e.g. Lucerne - Flüelen - Göschenen - Bellinzona - Zürich) 
Lac Leman (Montreux to Lausanne) 
these ships are covered by a Swiss Railpass. Eurailpass offer here just a discount 

Lake Brienz or Lake Thun near Interlaken have boat/ferry aswell and these are covered by both SwissRail & Eurail pass 

Zurich to Chur is not the Bernina Express route! The Bernina Express runs from Chur to Tirano on the Italian Border. Depending on your arrival time in Chur I recommend a return trip to Samedan which is a spectacular ride (the Bernina Express goes this way). A shorter alternative is a trip up to Arosa (sit on the right when leaving Chur). As the post above says travel to Montreux via Andermat (plenty of places to eat here) but use the local trains. You can hop off at any station that takes your fancy and carry on one hour later. We don’t recommend the Glacier Express (unless you want a spectacular but pricey restaurant car meal) as this train has an expensive supplement and requires advance reservations. In my opinion the local trains are far superior as they usually have some older carriages where you can open the windows to take photographs.