Having recently written an AAR about France, I feel like I should say something here. Is France OP?
France has the ability to succeed in whatever they set their eyes on. No single nation on Earth can truly stop them. Russia, potentially, could, but by the time they become truly scary, they lag behind in tech. Plus they are quite far away.
In my AAR, an alliance web between Spain, Portugal and Austria kept me somewhat in check, but that may have been due to my being overly cautious. If the AI gets beat up early (say by an alliance between Castile and Burgundy), they can lose a lot of traction.
The main question, to me, is: do you mean OP in terms of historical potential, or in terms of game balance? Historically, France really was a monster. It took a lot to get them to bend. So, in that context, I don't feel like they are OP.
In terms of game balance? Probably, yes. Their massive tax base means that it will take half a dozen wars or more to take them out of the running. Their ideas and traditions, along with their massive Manpower, make them into a combat monster.
Do I mind? Not really, I guess. Whenever I play as anyone close enough to feel their presence, it gives me an added incentive not to p**s them off, or become a target. France being the BBB tends to make my game better, because I have to be at the top of my game at times like these.