Does having low Testosterone affect how deep your voice is?

Voice deepness happens during puberty, but it can't be concluded that having highly deep voice is related to testosterone. Ronnie Coleman has very high pitched voice, but I wouldn't doubt his testosterone levels. He's 8 times bodybuilding mr.olympia.

If so, I'm assuming low testosterone leads to a higher pitch?

yeah it also can separate the alphas from the betas

Yeah basically.