Re: Levels of VSH genetics
A friend of mine has been producing queens from VSH breeders for several years - all of his hives from honey producers on down to drone hives and mating nucs are now headed by descendants of II VSH breeder queens and have been for some time. It would be reasonable to assume that the wild population in his area has some component of VSH as well. So, probably there is as much VSH in his operation as one could reasonably expect in open mated bees.
But there are still hives that do better or worse. You still do mite counts and replace queens in under performing hives. Nothing really changes except that with the same cultural practices (whatever they might be) mites won't be as problematical as they might be otherwise. So they just do better in general on average.
As you might imagine I use some of his queens (and cells) and they are very good quality, but not magical bees. Their performance still has as much to do with my husbandry as any of the others.
Don't let what might be best prevent you from doing what will work.