So I changing every character in Sunset Valley, I give them different clothing for example. But sometimes I see at the relationships that there are supernaturals. But this time I don't want them to be in the city. I tried to cure some with the elixirs and I turned off story progression, but I still see some supernaturals.... How can I prevent this from happening? I don't want to delete supernaturals, just turn them into humans.

I think in settings, there is a population control on the last tab where you can disable the different supernatural types. I'm not sure if it will get rid of them completely, but I'm positive it will stop them from spreading, and I think it will rid them completely if you change these settings before you even load the world, but I'm not sure, since I've only tried to do so with celebrity population control, which I discovered disables celebrities entirely if you turn it off before loading a world. Hope this helps!