We have ten nights in April. Looking at flying into Venice, spending three nights there, then two nights in Verona, two in varenna, then to tirano to catch the bernina express to spend a night in chur Switzerland (major bucket list train ride for me). Final night in Zurich prior to flying home. This will hit a lot of our preferences: Venice off season, smaller Italian towns, beautiful scenery. Is Verona the right spot to choose given the rest of the itinerary? Folks seem to think highly of it!
April is no longer Off-season in your Italy locations. Easter is early April, 2026, so try to avoid the week before and after Easter, if possible. Europeans love their holidays.
Lake Como has been discovered by the influencers, sadly, which we experienced this past spring. It's so beautiful, but the regional train from Milan to Varenna has been likened to a cattle car, so be prepared to stand for an hour. The train to Tirano should be fine. Be prepared for the ferries serving Varenna to be crowded, with lines to buy tickets and board. We bought our all-day ferry tickets at 7:30am, and used the ferries between 9:00am and 2:00pm, to avoid lines.
The Bernina Express route is incredibly beautiful. We used the regional trains, not the panoramic trains, which have more schedule options. Also, the regional trains are less crowded, don't require a reservation, and use the same tracks.
In Venice, one of my favorite places, we stay on the quiet back canals in the Cannaregio area. Here there are no crowds but plenty of charm, but just a ten minute walk to a vaporetto stop.
If you don't have an early flight, stay in Lucerne the night before. It's an easy one hour train ride, and the train station is in the airport.
I did digress from your question. I feel if you are aware of the realities on the ground, you can adapt and plan a memorable adventure.
Have a wonderful trip. Safe travels !
We spent 3 nights in Verona last Fall. We really enjoyed it.