I agree with the others about choosing to leave your main suitcase on the bus while visiting Venice and CT. It's easier but as pointed out not required. If you want to haul your bag in on the vaporetto and over the bridges (which are steps not ramps) you can.
In bigger cities (Rome and Paris are the ones that come to mind) you may be given tickets to use the public transportation system. I think in both Rome and Paris we were given tickets for 4 rides. Some we used with the group to get to a certain location, then we were on our own to come back to the hotel using the other ticket. One of the hallmarks of Rick's tours is that the guides work on teaching you travel skills including using public transportation. I don't know where you live, but I've never lived anywhere that there was a transportation system so I particularly appreciated the lessons!
If you are considering this tour my tips are to work on fitness so you are comfortable walking at least 6-8 miles. In both Amsterdam and Rome we went closer to 10-12 miles with the guide! I'd also suggest you have shoes you know can go this distance. You have to take care of your feet on this tour!
Do plan to arrive in Haarlem a day or two before the tour start date (as many days as you can manage) and plan to stay longer in Paris at the end if you can.
This is such a wonderful, wonderful tour! You will see SO much!