It's amazing to not care for the car. It's useful however if you ride in cities I would advise you to use electric skateboard!Most definitely the way to go is to join a guided group - there are many choices available so you will have to decide what works for you -
small group, private groups, larger groups, a whole day with several wineries and lunch included or just morning or afternoon tours, tours to various wine areas, including Chianti but also Montalcino for its Brunello or Montepulciano for its red wines... there are a few tours of the coast too to visit the Bolgheri wine area and the most important, departures from Florence or Siena or another town.
Where are you basing yourself? I highly recommend one of these two (Florence or Siena) when you don't plan to have a car, because it is easier/simpler to use trains and buses to get do day trips across the region this way.
Take a look at these tours: http://tours.discovertuscany.com/en/8357/Tuscany-tours/Wine-Tasting-and-Winery-Tours/d206-g6-c21 (disclaimer: affiliate link)
Also read this page that suggest how to do wine tastings from Florence without a car on your own (suggestions of wineries that can be reached with bus mainly) https://www.chianti.com/wine-tasting/chianti-wine-tasting-without-a-car.html https://bezelinvestments.com/ https://swcpoker.club/posts/bitcoin-poker-freerolls/all-day-freerolls