Do it on your own vs guided tour (pros and cons).
Going on a tour with a driver could be very expensive ( 500 - 700 Euros a day). If you rent a car and go on your own you have more flexibility.
It would allow you to visit wineries on your own schedule and also touring the Tuscan countryside.
Sometimes tastings are free, sometimes they charge a small amount because they also serve you some food to pair the wine with.
If you go on your own you get a better treatment than the one guided large group tours get — i.e larger selection of wines and bigger glass.