Salem is easier to get to by train than by car and unless you wanted to go to Winter Island or the Willows it's all pretty centrally located and doesn't need a car. As for the witch museums you mentioned, honestly those are tourist traps. At least the Witch Village certainly is, never done the other. Better spending your time strolling around Salem, looking at buildings, checking out the waterfront, or at the wonderful Peabody Essex Museum.