Possible trip to Brittany

Somewhere in the west, Quimper (aka Kemper).

I've taken the TGV to Rennes a couple of times from Gare Montparnasse to rent a car. Relatively close to Mont Saint-Michel, Saint Malo and Dinan.

We did the same thing as PharmerPhil in February: train from Gare Montparnasse to Rennes, picking up a rental car right at the train station. We based ourselves in Dinan and really enjoyed it, taking day trips to MSM, Saint-Malo (of which I was not a fan), Josselin, Vannes, etc. We intended to drive to Quimper for a day (which would have been a pretty long day, for sure, and started to make me think we should have split up our accommodations between east and west but I was so in love with our Dinan Airbnb that I didn't want to stay anywhere else) but we'd had such heavy rain the previous afternoon in Vannes (we could not even get out of the car it was raining so hard) that we decided to skip another long drive that might end up the same way.

Picking up the car at the Rennes train station was easy, with the biggest (but totally doable) challenge being the VERY tight parking garage.

Eef, I cannot advise regarding car rentals. But our recentish, loooooong and photo-dense TR below probably has some useful info.
Over on Fodors I go by 'zebec'.
I am done. The end.
https://www.fodors.com/community/europe/lappel-de-mer-a-southern-brittany-tr-also-paris-1723447/

Dinan is a good spot, we had three nights there a couple of years ago in our trips. Other options in close proximity would be St Malo or Dinard - all can be done as a day trip easily from the others, depending on where you decide to stay. Only 20 km max…

Quimper in the west has been mentioned, with a possible alternative in Concarneau, or somewhere nearby in a village.

Closish to Carnac is Vannes, lying at the gulf of Morbihan.

I would actually somewhat recommend to do a fourth stop somewhere along or close to the cote de granite rose, so in the north west of Brittany, since at least we felt it was the nicest part, and going from Dinan directly to Quimper will cost you the day, and you would miss out.

All places come with the side note that it could be better to take a place a bit more rural, since you have a car.

I think you can get a car at St Malo, which has a TGV stop, but will have to drop it off in Nantes or maybe Vannes then.

10-12 days is a good length, with my leanings going for 12. We had 10 nights, with four stays of 2 or 3 nights, and felt the „twos“ a bit rushed in hindsight…

Hi Quimper is a very beautiful historic city, which has the advantage of being lively in all seasons, and it is a very good base for very varied visits... Pointe du Raz, Pointe de la Torche (surfing in all seasons), Crozon Peninsula, fishing ports (Le Guilvinec, Audierne, Douarnenez, and other historic towns or villages, such as Concarneau, Locronan, Pont Aven etc.

Including my summer 2025 trip report here https://community.ricksteves.com/travel-forum/france/brittany-trip

I’ve not been to Quimper but did spend 3 nights near Carnac in a 2017 trip.

If I were you I would train to Rennes then spend 3 nights each in Dinan, the rose granite coast, finistere and then the south (vannes, Carnac, Auray) area around the gulf.

Then drop off the car in the most convenient spot to get a train back to Paris.

If you have only 9-10 nights, which spot to drop would depend on your interests. Here’s my take.

Dinan is a must. Keep that. Please find a link to a really great oyster and mussels shack on the coast in my trip report. I’ve been there 4 times between 3 trips. It is about 25 minutes from Dinan They are so casual that they encourage you to order fries from the next door establishment to complement your shellfish meal at their place.

RGC has the most natural beauty. The RGC walk is one of my favorite things I’ve done on vacation. The seafood is great and I’ve included a link in my trip report to an outstanding market selling local produce and artisan products. We cooked some of our best meals there.

Finistere has wonderful beaches, lighthouses, beautiful coastal walks and ww2 history focused on the battle for Brest. Brest itself is not worth your time but it is a great place to drop off the car and train back to Paris. I’ve linked to an outstanding museum about the battle for Brest in my trip report.

The gulf area is best for pre history sites. Carnac is cool but Gavrinis was my favorite. I’ve not been to Vannes but people seem to like it. I found this area less beautiful than RGC and Finistere but I may be splitting hairs here.

Please note that I likely spelled place names incorrectly but came close enough. The linked trip report contains more of the tricky to write place names spelled correctly.