As said on the post underneath yours, most of these spells can be really possible. It is the believing matter that people have a problem with, some people lack belief when doing a spell, so the spell doesn't work or doesn't work exactly how they wanted it to work.
Vampires/ Werewolves would live in the Astral Plane if anything, sense the astral plane is basically made up from the mind of what we invision. What ever fairytales and other things that people bring into mind can exist in the astral realm.
Anyways back onto topic, transformation spells of any kind will not work (as said above, you can not change your DNA using magick). Spells that makes your gain or loose weight will not work. Spells that control the elements will not work (this is because the element are more powerful then we are). We can only work with the elements.
There is like a whole list full of spells that couldn't work, I'd suggest reading more about magick...not what you would see on the television or in the "Fantasy" section of the site.