Its genetics mostly. My relative is mouth breathing when he sleeps asf. His mouth ends up being open and his head is thrown back. But he has a sharp asf jawline at low bf%. He has other problems though, where mouth breathing could affect. Its not only your tongue position, there are lots of factors. If you have troubles breathing through nose as a babycel, it can lead to bite issues and those will later affect jaw growth imo.
It all boils down to teeth treatment as a kid imo and parents not being able to afford good orthodontist. My insurance covers free dentistry, although only in government funded clinics and they fuck up everything there. They are stupid, they extract teeth for no reason, they can't really tell what is wrong and what solution do you need. A bad doctor is the best way to get those issues. I think there is some truth to mewing. Its not going to give you chad face now. But if you pay attention to babies and kids. Do they breathe properly? Breastfed or bottle, which matters. How they sleep, their bite issues. If as a kid you get good tongue posture + nose breathing + properly chewing food + good orthodontist without unnecessary extractions on top, it can lower the chance of issues.
Extractions matter the most imo, average orthodontist knows shit, and they always extract teeth for their stupid treatments. Dunno about other places, but here we have braces analogy for poor, free clinics advise them, although they never help and always require extractions. They don't really know the science behind it, and just go with universal advice for everyone, and there no one to blame later, although i think they know their meaningless solutions affects face aesthetics. If your teeth don't hurt you fine bro!
