Bernini Express from Chur to Lugano, then on to Venice and Rome!

Last question first.

We have tentatively booked two nights at Hotel Delfino in Lugano, but I know it would be less expensive to stay in Como - could we realistically fit a trip to Como at the end of the bus from Tirano to Lugano?

Not really, the bus arrives in Lugano at 5:30 pm, too late for that. The bus is nonstop from Tirano to Lugano, so I don't believe you can get off in Italy, You will travel along the west shore of Lake Como to Menaggio, then cut over to Lugano from there.

There is no luggage storage at Como S. Giovanni station, so that makes it difficult to stop over on the way Venice. You could spend a night there though and take a boat ride on the lake from the Como lake front.

As far as a rail pass, no. You need to buy seat reservations for a TGV from Paris or CDG to Lyon, on top of the rail pass, as well as EC train from Como to Milan, Milan to Venice and Venice to Rome. If you are not stopping in Paris, see if you can get the continuation to Lyon included in your airline ticket. Lyon to Geneva is a TER, which is unreserved and always the same price.

In Switzerland, the nominal fare from Geneva to Chur is 112 CHF per person, but beginning 60 days before you travel, you can buy a Saver Day Pass for 49 CHF per person, the price goes up as you approach your travel date, so buy when you are 60 days away from your intended travel date. Bernina Express requires seat reservations, so buy that ahead as well.

In Italy, you can buy nonrefundable advance tickets. Right now, you can get a direct train from Lugano to Venice for 87 EUR for 3 people. Venice to Rome, for 128.70 EUR. These tickets will include the required seat reservations.

I can't answer the financial question (do your own adding up ☺).

As far as Como is concerned. There is Lake Como, and the town of Como, do not confuse them.
The town of Como is the largest place on the lake, but not the prettiest. Most tourists should stay elsewhere.

The bus from Tirano to Lugano is only once per day (restricting your timing). It runs down the west side of the lake as far as Menaggio, then cuts across to Lugano. Your options are.
1) Bus Tirano to Lugano, optionally stop off for a night in Menaggio. Second night in Lugano. Train onward to Milan.
2) Bus to Lugano (overnight), then train south to Como town (overnight).
3) Train from Tirano. This goes along the east side of the lake. Stop off overnight in Varenna. Train onward to Milan.

I vote option 1 or 2 (I downvote Como town). 1 gives you Lugano, 3 gives you more Lake Como, and more departure options.

From Milan, train is easy to Venice and onward to Rome.

"we plan to purchase 1st class tickets" - don't bother. 2nd class is perfectly OK.

Thank you so much, this is very helpful! To Chris F, i like your option 1, which is where we were leaning, so thank you for the info! I have been to Como (and down Lake Como) before and wanted a repeat visit but with the 2 night short visit, we’ll just stay in Lugano. I appreciate your insight!

Thank you Sam, this is very helpful! We’ll probably stay in Lugano both days, with maybe a day trip on Lake Como and back. Thanks for the train options, that was next on my roster so i will book that next!

One other newbie question - if we have purchased a reservation for the BEX train from Chur to Tirano, do we also have to purchase a reservation for the bus from Tirano to Lugano?

Yes, you need to reserve the bus from Tirano to Lugano. AFAIK you normally do it at the same time as you reserve the Bernina Express seats. The two work as a connecting service.

Well bummer, I didn’t know that and already booked my reservations from Chur to Tirano - perhaps there is a way for me to look up my reservation and add that leg - good lesson for me!