French autoroutes are a great but fairly expensive way to travel, speed limit is 130kph in dry weather, think it's 120kph in the wet. Rest areas and service areas are clean and good value. Lots of cheap places to stay like Formule 1 hotels, not the height of luxury, but cheap, clean and convenient for a night's kip. If you have the time the RN (A roads) are more scenic and interesting but substantially slower. It is obligatory to have at least one disposable breathalyser kit with you - but there's no fine for not having one. Hi-Viz waistcoats should be accessible from inside the car, one per person.
It's not Germany, so you can't go crazy, but you'll probably find most traffic going a bit faster than 130kph - there are urban rumours that they can analyse your peage tickets to see if you've exceeded the average speed, but I've never heard of anyone it's ever happened to.
Cheers, Dave