Reading between the lines, I figured that you had assumed it was a car ferry between Falmouth & St.Mawes. I suggest that you try and follow the intended routes on Google Earth. When they say 'car free village'; what they mean is that visitors will not be able to drive their cars through the village. (This can also apply to locals). What will happen is that you drive to the approach to the village(s) and will be directed to a car park. When (if) you visit Fowey, Polperro & Looe, it will become quite obvious that the narrow streets, laid out hundreds of years ago and all lined with cute cottages, would simply be impossible for modern day traffic. If you Google the name of each of these and the word 'images', you will see what I mean.
You might also like to see this place en-route or as a day trip:> http://www.edenproject.com
You might wish to consider visiting these gardens (which are just SW of Falmouth) whilst staying at Marazion:>http://www.nationaltrust.org.uk/glendurgan-garden/
and www.trebahgarden.co.uk
I have not visited these gardens but they seem to have a good reputation and they are right next to each other. You may even have time to take the foot ferry from Falmouth to St.Mawes on the same day.
When in Stoke Gabriel, you should be able to take a ferry down to Dartmouth. Totnes main street has some wonderful old buildings.
Salcombe should be another place at the top of your list. Torquay & Paignton are congested.
BOA is the rail code for Bradford-upon-Avon & BTH for Bath. It only takes 12 minutes on the expresses (Portsmouth > Cardiff) & about 16 on the stopping trains. This is likely to be more convenient than trying to drive into Bath. Not sure about parking near BOA station. Last time I drove to Bath, I got stuck in a jam and did 1 mile in 20 minutes!