I would say R'n'B has more sexual themes than rap, but it is quite common in both genres. I'm not a fan of these songs, I prefer more original artists like A Tribe Called Quest, De La Soul and KRS One. These are all rap groups from the 90's and they rap more about life/politics and less about sex. I find their lyrics funny too :)

Many are about sex. Topics for rap music vary from the "unlovely" (violence, misogyny, drug use, hedonism, etc.) to some things that are very positive, like love of family, romantic love, changing one's life, etc. If you want positive rap, my teenaged son suggests listening to Brothatone or Canon.

Many songs are.

Most of all

I'll admit it mostly about sex maybe the wont say it right away but some will led to sex so yeah mostly