Speed cameras keep popping into the discussion...
Just like the UK they're not something to get overly worried about as long as you try to obey the speed limit...however there's not much flex above the placarded limit and I wouldn't recommend really burning it up on the peage or autoroute.
If you are caught really flying ( say much above 160 in a 130 the penalties can be spectacular ( in extremis that can include handing over car keys)...
Despite some previous comments there really isn't one typical camera type that you need to keep an eye out for, there are various versions dotted around.
Some are highly visible, some are even signed (permanent ones used to have to be) , some are hidden away and are mobile -as I know to my cost 😯-...sometimes the Gendarmes run things the old fashioned way with mobile checks using the good old fashioned speed gun, especially on popular routes...
I-Spy guide to French cameras here:
english.controleradar.org/french-speed-camera.php
Locally we have all the generations photographed, occasionally you'll encounter the ones hidden in a car plus occasionally they'll put small mobile boxes out by the side of the road, for some reason those are usually secured to handy railings or lamp posts..😉