Where should we base ourselves in Tuscany?
 

I assume you've planned the exploring you'll do from Lucca using public transportation. I would find Lucca a bit limiting for two weeks using only public transportation. But that's me, and I admit I'm not a big fan of Lucca.

For the second two weeks, it would help if you had a sense of your priorities. For example, even with a car, much of Tuscany and most of Umbria would be a bit too far for day trips from either Arezzo or Montepulciano. i.e., Chianti, Siena, San Gimignano, Volterra, Perugia, Assisi, Spello, Spoleto, Todi...

If it was my trip, I'd probably pick three destinations to keep the driving times down. I like Arezzo but not as a base for several day trips by car. (You'd have to pick lodging with very easy ingress/egress plus parking, but there could still be rush hours to deal with.) I really like Montepulciano, but as a base for day trips it only works well for exploring the Val d'Orcia, a little bit north and south of the valley and a tiny part of Umbria around Lake Trasimeno. If you look at a map, most of the larger roads are north-south. It takes more time to go east-west.

If you're using Google Maps for driving estimates, add at least 10% and more if you're traveling in high season.

If you haven't driven in Italy before, you need to learn all about ZTLs.

https://mominitaly.com/ztl-in-italy/

Agree with Jean, perhaps Lucca, Siena (or somewhere in the Chianti region) and Montalcino/Montepulciano (for Val d'Orcia) would optimise your driving.

I go every year to the same apartment hotel in Castiglione del Lago on Lake Trasimeno (been doing it for over 30 years). You can visit a whole range of 1 day or half day trips from there by car including Arezzo, Assisi, Chiusi, Cortona, Montelcino, Montelpulciano, Orvieto, Perugia, Siena, Spoleto, Todi as well as around the lake.

uktravelover, could you please link that apartment hotel?

Residence Castiglione- it has studios, 1 bedroom apartments and bedrooms only. A good continental breakfast with rolls, croissants, ham, cheese fruit, fruit juice and yogurt available. Cappuccino, expresso or tea made to order (not a sel-service machine). Has a swimming pool, parking. It’s close to the lake or you can walk uphill to the town or drive up and park. Closest supermarkets are 2 minutes drive.

We enjoyed spending four nights in Lucca but do not recommend it as a base. It is too far west for that. Look at Siena and the Chianti towns on SR 222 and or Cortona to use as bases. For Umbria, look at Spello where we spent two wonderful weeks.