We are departing for Cap d' Agde on Friday with an arrival on Saturday night. It has been three years since our last visit so we'll be particularly observant for any changes (i.e. restaurants, nightclubs and new construction) that have occurred during that time frame.
I promise to report anything of note on this travel forum.
If by "all adult" you mean a boutique hotel in St. Tropez there are several. We've stayed at the Pan Dei Palais right in town and found it wonderful. The accommodations and price will keep the children and summertime college-age party crowd out. I just used a well-known "trip advisor" website and quickly found this and some other St. Tropez high-end properties.
Well over fifty years ago the late director Roger Vadim shot footage of Brigitte Bardot at St. Tropez while filming And God Created Woman. Since then, generations of beach worshipers have returned looking for her contemporary equivalent. Probably the most famous nude beach or plage in the area is Plage de Tahiti. No doubt there are Europeans who access this forum that could recommend other favorite spots to get an all-over tan.
Most of the time we've spent on the actual Cote d' Azur our goal was more mainstream sightseeing than simply visiting nude beaches. It should be noted that St. Tropez is well east of Cap d' Adge, much closer to Cannes and Nice.