Loved Lucca. Second that as a base.I have spent a fair bit of time being slowly nomadic in Europe over the past year.
It sounds like you are looking for a quiet time, in which case I would suggest Portugal or Tuscany would both suit. Sintra is a beautiful town, quiet and peaceful with a lot of hikes and tourist stuff around but also 40 minutes to Lisbon by train (or 15-20 EUR) in an Uber away. Also has a lot of genuinely world class coastal attractions like Praia Adraga, Praia Ursa, Cascais, Estoril all about 20 mins way (under 10 EUR by Uber). I'd stay there over Lisbon personally, though Lisbon also great if you want more action.
The Algarve is naturally also a wonderful place to take it easy, different vibes in different towns so easy to find something that suits.
Can also reccomend Lucca in Italy as a great place to spend a few weeks or a month. Great character in its own right and decent connections to other Tuscan cities like Florence, Pisa etc. Not far to the beach or mountains if you have a car.