My friend and I (both in our 20s) will be travelling to Italy and a little of Switzerland in June 2018. We will start our trip with a week around Lake Como. Upon leaving Lake Como, we would take the train from Varenna to Tirano. Then, we would love to take the Bernina Express from Tirano, Italy to Chur, Switzerland. Once we arrive in Chur, we were thinking of staying the night in Chur, then leaving for Venice the next day. Would it be advisable to travel from Chur to Venice in one day? Or should we take a night stop along the way? It looks like there's a FlexiBus bus from Chur to Milan, then train to Venice. Or, we could take the Bernina line back down to Tirano.
Are these buses good for travel, or would train be better? Either way, which route would be the best to get to Venice? I don't know if it makes a difference, but we would each have a 24 or 26 inch suitcase. Thanks!
Train back the way you came would be easiest. You don't have to ride the actual Bernina Express train, which has reservation fees/supplement, but you will have to change trains a couple of times. But your youth and strength means you should have no trouble handling your bags. If you can get it on and off the train, you can take it.
There is about 100 meter walk between the stations on Tirano. If you take a bus to Milan, check where it drops you. The main bus station in Milan is long way from Milano Centrale station, which means a transfer on the Metro, perhaps with a train change, or a taxi. The train from Tirano will be to Milano Centrale, so then it is just a track change.
If you're checking train schedules online for the whole route, DB is suggesting a morning bus from Chur to Bellinzona, not all the way to Milan. The bus arrival is right by Bellinzona station (4-minute walk). Trip time is 7.5 hours and only the 1 connection for the 7:30 departure, otherwise 2 connections.
The train route back via Tirano takes 10 hours & 2 connections with an 8:30 start. You very well might like to see it all again, in different light, or weather, or sitting on the other side of the train.
Your suitcases could be smaller, so don't be tempted to pack them full. About 25 pounds is all most of us can handle easily in multiple situations. See also www.ricksteves.com/travel-tips/packing-light.
Now that Laura mentioned it, that is a good way by using the Post Bus that runs about every hour from Chur to Bellinzona. That bus has a required reservation, but will short-cut some time and still have nice scenery, just a short tunnel along the way. Buddy did it a couple years ago, we went to Zurich and flew to Venice, and he left at the same time on the bus and we only beat him by an hour.