Have done this trip many times and have not once been asked for documents (8 times in total). So maybe I am just lucky.
That being said, my trip takes in Le Havre (LFOH), Nevers (LFQG) and then Marseille. Le Havre does not have much to see but it has customs, fuel and crap weather. Fog can hang around for days. Nevers is a great little airstrip but the tower is not manned during lunch (12-2) nor on weekends which means no fuel avbl. Also, French only on the radio outside of tower hours.
I use the Jepp VFR charts and they have all the VFR reporting points on them.
Alot of military airspace and restricted areas. Nuclear sites are marked on the chart and you normally have to be a minimum of 1-2 miles clear of them.
I don't know what your plans are but one trip that I can highly recommend is down the west coast via Nantes, Bordeaux, Biarritz then across the Pyrennes (spelling?).
I like the French ATC and I hope you find the same.
Have fun.