Southern Brittany home base

We stayed in Auray for a few nights. Interesting town and picturesque.

Another option is Lorient which is mid-way between Vannes and Concarneau so easy to visit both of them from there. Of course if you're going the first week in August you might have problems finding accommodations because of the Interceltic Festival. Another option if you like smaller towns/villages is Pont-Aven. I only visited for a few hours but I wouldn't mind staying there for a few days.

Vannes is a nice town with a medieval center. It is very quiet at night and walking thru the medieval part feels a little strange with nobody else around, although some restaurants are open. If being on or near the water is important then note that Vannes is actually up a channel to its harbor; there is no beach in Vannes, the bay is is a ways away.

It really depends on your wishes for a town or a city (active night life or not important), along the sea or not, etc.. Vannes and Concarneau are good options, Pont-Aven or Auray too. Are you traveling in summer ? If not, you could consider places like Quiberon, Locmariaquer, Bénodet...

I stayed in Vannes and was happy with the choice. I found a nice Airbnb within a ten minute walk of the center. Vannes has a surprisingly large medieval center, complete with ramparts. Next to the old center is a large port area (not industrial) with outdoor cafes.

Vannes is within easy driving distance of Carnac. I also visited Cairn Gavrinis from Vannes. It's a neolithic passage tomb similar to Newgrange in Ireland. It was only discovered in 1988. It's on an island and you get there by taking a ferry tour from Larmor Baden (close to Vannes). The tour is all in French but worth it to see the Cairn, partially submerged henge and the Gulf of Morbihan (the tides are amazing).

I stopped in Auray and liked it also. It was like a smaller version of Vannes. If you prefer a smaller town atmosphere, that might be the better choice. It's also convenient to Carnac and Larmar Baden.