I think the third one is closer to accurate, because Springtrap IS somewhat crouched when he jumpscares you, he isn't standing perfectly straight. But the suit was also made for humans, which means it can't be THAT tall--unless the specific human it was made for, William Afton, was quite tall. (Which he was, we see in several minigames that he's the same height as the animatronics, which are all around 7 feet tall.) I would personally assume Springtrap is around the same height and that the suit can be adjusted slightly for shorter humans.