Vampires, Witches and Ghosts

You're 100% correct with Paranormal stuff. If you don't use the Haunted Lot trait, you will not see a single ghost. (Except for the Sims BG ones that appear when a Sim dies, but that has nothing to do with Paranormal)

I'm not sure if deleting the Sages will cause new ones to generate and respawn but with Realm of Magic, you barely notice the magic outside of the Magic Realm. You may still see the characters walking around, but they will pretty much act like normal Sims. Heck, even in the magic realm the cauldrons tend to be used for mac and cheese rather than potions. To be honest, I wish the use of magic was far more noticeable since I play occults like 99% of the time.

As for Vampires, you will get a text from Vlad welcoming you to the neighborhood and vamps may use their powers when hanging around lots as @Nushka said, but there are ways to prevent them from attacking your sims and breaking in. Disallowing, using garlic braids and wreathes.

@MeowchaFrappe @Nushka Thank you guys so much. this was very helpful!!