If you are looking for freedom, a group tour might not offer that as they are usually very pre-planned in order to keep pricing down. I would reccomend either a private tour or just hiring a private driver who knows the area a bit.
As for what to visit, Chianti is a very broad term. Florentine Chianti is usually regarded as the area about 40 km around Florence. Here you will find good wine and a more relaxed countryside experience.
Up to 80 km out is the Classic Chianti area, where the wine is more expensive but slightly better (also depends on personal taste). Both areas have stunning views and plenty of winneries and farmhouses to visit.
I would definetly also visit San Gimignano.