Rent a car or take a bus?
Although every town afore mentioned is easily accessible by bus, some of the attractions outside the city walls may be more difficult to reach without access to a car.
If your main goal is to visit and tour vineyards, walk through medieval towns, explore some historical sites, and enjoy various artistic and gastronomic delights, then travel by bus will be a sufficient form of transit.
However, if a more in depth tour of Etruscan sites of early Roman churches is in your itinerary, renting a car may be a more reliable form of transportation. Taking account for holidays, weekends, and varying bus schedules, mostly everything is accessible by bus - and if a bus is not available, there is always a taxi service nearby.