When I was in Venice in May, I had a 25 inch bag & backpack. We stayed near Piazzale Roma and only one bridge to deal with. That experience is my motivation for COO next time 😄
You mentioned that your last train segment was a regional train. Did you have to make a change?
I'm just starting to research the train from Rome to Venice and thought the Frecciarrosa trains were direct to S Lucia station? I'm finding the Trenitalia website a little confusing.