Speed Limit: I think you should learn how to use your cruise control. Speed limits are very logical and predictable but sometimes speed limit signs are gone (e.g. entering a town). Typically, there is a sign, something to the effect of "speed is electronically controlled for your safety" about 1 km (varies) before speed cameras.
I've heard, but don't know, that the grace factor is 4km/hr - which isn't much. I think you're better off sticking as close to the speed limit as possible. The ticket goes up in price the more you exceed the speed limit.
We've used apple maps mostly as our GPS in Europe. It says where speed cameras are. Police still set up speed traps with a portable detector, so you can't rely on signage or a GPS all the time.
Toll booths: I've had more trouble using credit cards in France than any other country. I've (more than a few times) gone through every credit card, twice before a toll booth accepted my payment and let me go. I've had the same problem buying metro tickets, gas, etc. with my cards in France.
Carry some cash with you (no more than 20-euro bills, preferably smaller), and go through a lane with cash and card as an option. This will be my first time with a tap technology card in France (last trip was 2018, next is September). I've used my tap cards in Scandinavia, Finland, Estonia, Germany, Chechia, Hungary, Austria, Spain and Italy (others?) since Covid, with excellent results. I'm expecting the tap option is going to make getting through a toll booth much easier.
Limited local traffic areas haven't been a thing in France (I don't drive in Paris). Italy has them in every city. In France, you will see no entrance signs on roads regularly, but that's for all traffic because it's a one-way road. If you can't drive somewhere, it's been pretty obvious.
Getting Gas: The most convenient gas is on the major toll roads. They have "truck stops" along the road at regular intervals. They are always staffed. If you have any issues with paying, there's a person inside who can help. The cheapest gas is at supermarkets. They have some hours where they are staffed (a kiosk with a person where you can pay) but most hours are done automatically with your credit card. Typically you fill first then pay, which seems odd coming from the US. Again, I expect it will be much easier with a tap card.
I've been to Lyon, Bordeaux and Strasburg. In bigger cities, I typically park my car in a parking lot and leave it until I'm done with the city. In Lyon, I picked up a car on the way out of town and never noticed any local traffic only areas. In Bordeaux, I dropped my car when I got there. They seem to be as traffic friendly as most US cities. In Strasbourg, I parked near the train station and walked in. I could have probably found something closer to the center. The further from center, the lower the cost per hour/day.