There are four anatomy types - penis, vagina, chest, breast. I recommend only using SimpleGens because it will be updated going forward. You CAN use both RealGens and SimpleGens in your game at the same time without conflict or errors. RealGens is deprecated and unsupported (outside of major necessary updates). The SimpleGens mods continue to receive upgrades and updates.
SimpleGens is a more recent set of anatomy mods I released last year. RealGens is a family of anatomy mods (penises, vaginas, etc) I released a few years ago. This post is intended as an FAQ/download directory/info repository for anyone using my mods, whether you're new or you've been here since the beginning.