Yes and no. If you stay close to the castle, then yes, it stays vanilla. Personally I like chocolate, but who cares? Anyways, if you travel far enough where the terrain begins generating, as far as I know, it will become Tekkit. But you're gonna have to walk for a PRETTY LONG WAYS to actually get to that point, so if you go the extra hundred miles, then Tekknically (pun) you should be ungriefable.