Suggestions Sarlat to Arles

PKV,
You can drive it in a day. Viamichelin says about 5 1/2 to 5 3/4 hours, but I would add a good hour or two for gas and meal stops. You might look at the route on ViaMichelin .com and see if, on their recommended economic route, there are places you may want to stop for a bit of sightseeing, such as at Rodez. Total distance is about 250 miles.

And I am happy to see you are spending 8 days in the Dordogne area. It is worth at least a week. Enjoy!

We drove Sarlat to St Remy
It took about 6.5-7 hours
Not sure of route we took but we did see the Viaduct du Millau on the way

We drove Provence to Sarlat a few years ago and stopped for an overnight in Carcassonne. We arrived late afternoon after most of the tour buses had departed. The Cite feels magical in the evening and early morning. We stayed at Hotel Donjon which is one of only two hotels actually located in the Cite. The hotel sends a shuttle down to the parking lot to take you to the hotel. Between Provence and Carcassonne we stopped for a mid-day break at the Carmarque Ornithological Park which in September had hundreds of pink flamingoes. No restaurant - pack a picnic for that stop.

Between Carcassonne and Sarlat we stopped at Saint-Cirq La Popie for lunch and an hour or so exploring the village.

In Provence we stayed at La Bastide in Saint Didier. La Bastide looks like the sort of place that a movie scout would choose for a film set in Provence. It has a pool which you might enjoy - Provence was really hot in September. There were a couple of bistros in the small village.

I'm excited for you, we spent a week in the Dordogne in October and loved it. Arles is a 5 hour drive but I'd recommend an overnight in Carcassonne. It's crowded during the day but spectacular at sunrise and sunset.

There are basically two routes. I have taken both a few times

The one via Toulouse-Narbonne-Montpellier which is, 45 minutes after leaving Sarlat, only highways (A20-A62-A61-A9)

The one via Rodez, the Millau viaduct - Montpellier which is in its first half on country roads, national or departmental.

The first takes you through the Toulouse ring road which can be congested, and then through what we call the "Two Seas Autoroute" passing near Carcassonne before reaching the Mediterranean coast (you will see the medieval city on the left from the motorway)
Depending on the day and time there can be quite a bit of traffic on the A9 between Narbonne and Montpellier.
The only places to stop along the way for a break or lunch are on the highways in rest / gas stations areas

The second option is more "green" and scenic with some sections on winding country roads up to the A75.
The possibility also to go to the village of Conques between Sarlat and Rodez

https://www.tourisme-conques.fr/en

The section on the A75 is quite scenic too.
In my opinion it's a more tiring option from a driving point of view and can be longer because it encourages you to stop, but not as boring as the first which is just a series of highways.

Carcassonne especially at night is fantastic, don't miss it! Great views of the old city from the road that leads through the wall (Porte d’Aud?) and down towards the river on the west side. On your way to Dordogne you might want to stop at Oradour-sur-Glane, a village frozen in time after a NAZI reprisal. Seems like you are going very close to the Loire valley, are you planning to stop at least Château de Chenonceau? It was our favorite, along with Chaumont sur Loire.
-Bruce

Thank you all for contributing and the good information!
Merci beaucoup!