The Genesis 1 and 2 items would have all been installed with DIM, and it's easy enough to use that to deinstall them. Genesis 1 though is really useful for creatures, as well as being the only generation where all the clothes fit both genders. Also Riversoft has a script now over at DAZ that will convert Genesis 1 clothing to Genesis 8. Anyway, your choice.

V4 and earlier are all over the place, some was under DAZ libraries, but most were in the Poser Libraries under runtime. Getting rid of those would be a pain, but the good news is they didn't take up much space to start with. You can knock out pretty much everything under /runtime/libraries/materials since most of that is not usable under DAZ.