Hi
Autoroutes are worth using - not all of France is a scenic wonderland, and the RN (Routes Nationales) will often wind through less attactive parts of towns via multiple roundabouts.
Get a toll gizmo
https://www.bipandgo.com/en. This takes the payment by direct debit after your trip, and enables you to drive through the fast lanes where the barrier goes up as you drive through. Also great if you are solo in a RHD vehicle.
Some motorways are now running with overhead vehicle plate detection, ie no toll barriers. I suspect most roads will be like this in 10 years. If you have the gizmo then it's detected by the gantries and taken automatically. If not it's a faff to log on and pay.
In a Cali you should squeeze under the 2.0m bar for Class 1 tolls. Take care, especially if you have bikes on the back, as some road underpasses have very limited headroom.
Use the aires on autoroutes, good facilites, picnic areas, playgrounds. You can forget about potholes, nearly all roads are built and maintained to a far higher standard than UK.
I've never had a crit air sticker in dozens of journeys, no problem.
Keep high vis and triangles in the van for emergency use.
Remember that drink driving is a major issue, and you can be stopped without cause for a test. It's just not worth the risk.
Usally plenty of free parking in small towns and villages - they want your custom.
European breakdown insurance - I recently renewed competitively with Aviva+RAC, cheaper than main RAC site.
The Cali is fairly secure except for the sliding window by the stove - this can be punched or slid out so someone can reach in. After mine was lifted, I fitted an aluminium angle inside to prevent this. Beach car parks seem especially prone to theft - but generally a safe country.
I hope this helps. Bonnes vacances.
