I have the different Story Progression mods that revolve around the occult sims (vampires, slayers, werewolves, and so on). I recall there was a way if you wanted to keep a certain sim as a vampire or the type occult they are, to keep them from being "cured". Where can I read about these different settings with the different NRaas mods (Story Progression, Master Controller, and so on?

I think the setting you are looking for is this one.
Under Sim Options, Personality: Allow Occult Change.

StoryProgression-Interactions#Personali ... ult-Change

On a side note, I believe that the leaders of occult groups like the Lestat, Dracul, Feral etc are immune to being cured, although followers can all be cured or killed, depending on your settings.