Thanks for your answers but I want to keep gens because I want to have the possibilities to use sheer or skinny materials as cloth.
I looked in the cloth parameters and changed the “fit to Genesis” to “fit to genesis genitalia”:
General>Transforms>Misc>Fit to: Genesis genitalia
But it did changed anything.
I grouped Genesis + genitalia as suggested by Larsmidnatt but I didn’t found the way to manage collisions.
Do you have some tutorial I could use to manage my issue?
RESOLVED: I use the “Mesh Smoothing” modifier and collide with gens… Working fine!