When it comes to humans in FNaF, it's not that simple to idealize a voice, as they've never been explored so much. It's not like the animatronics, which have been explored, have references, there's crucial information about, and so on. Humans in FNaF are "complicated"; however, in my view, this opens more doors for creativity. If you're going to audition for any human, regardless of which one, be creative and let loose! Bring out everything human in you and really embody the character. You can audition the way you want, with the text and lines that you find interesting.