I'm literally just curious... Which one do you type? I recently found out that the American spelling is "whoa." However, I type "woah." In my opinion, if you're trying to tell someone to stop in an interjection, you'd say, "Whoa!" However, if you were amazed at something, you would say, "Woah!"
I’ve never in my life heard someone say “Whoa” and if I did, I’d probably lose all trust I had for them
I'd say for me, it's pretty much what you said I'd even pronounce them differently, though. Woah = Wow! (positive) /wəʊ/ Whoa = Slow down/Oh my god! (negative) /wɒʊw/ I once read a story written by someone who thought it was spelt "woe". It was painful to read (even though it was a good story). "Woe", she said, looking at the pile of Christmas presents.
That will give me nightmares earsofjoy: It seems like most people use woah, too! I've never seen a woe though