Relative to France there are fewer campsites in Baden Wurttemburg and they do get very busy in August - particularly in the south of the BF the closer you are to Freiburg, Titisee, Todtnau, Mustertal and the Feldberg.
I'd do a search and see if you can book a site online.
Dont forget whilst down there to do the Kandel, the Glottertal and the Route De Ballon - all as nice as the B500. I also like the road from Todtnau to the frontier with CH. A good run is Titisee over Feldbergpass onto Basel then up the Route de Ballon over to Colmar and back to Titisee.