Asking permission usually is quite positive - especially on a bike. Less problematic to wild camp in less populated areas but campsites are fairly numerous and cheap. The Michelin maps that I have for France do not depict camp sites. Depends on the map scale of the Michelin. They are sufficiently commercially-savvy to realise that followers of the Tour need space to sleep.
Prices are lots better than Germany.
You will miss a lot if you do not have even the basics of numbers and pleasantries. Well worth making the extra effort. However, it would be a 200K trial to get there. The fly past by the riders gives the colour and sparkle to the day. It is the festival atmosphere with the crowd that is worth the effort though since you will be assured of seeing next to no racing as the riders pass the TV or a radio will fill in the picture.