So I saw a model in the loading screens, one added in of a man in heavy Stalhrim armor, and the longest hair option. The hair was showing at the front despite the helmet. Does this happen for your character if you pick the longest hair option and certain helmets?

No. The loading screens are special models made specifically for that.

I've never had it appear like that for any of my long haired characters, so I don't think that it's possible.