@Atreya33 I'm not sure about hair growth for NPCs, but NPCs of both genders definitely generate with various body hair presets, including way more chest hair and back hair on women than would ever be realistic.
My saves are weird places anyway, with plenty of occults and ghosts and strange happenings, so I feel like the extra-hairy sims fit in okay, but I do wonder why there isn't a global "disable for random" available on the body hair presets (or hair growth if that's what it is).
Social Bunny affects relationships of sims who are on each other's contact list in the app. If one sim has the app and not the other, or even if they both have the app but neither sim has added the other to their contact list, it won't affect their relationship.