”Mewing” is just normal tongue posture. It
will not improve your jawline. Usually it’s the reverse: if you need to “mew” / put your tongue on the roof of your mouth consciously and if you naturally snores it’s
because of a problem.
Problem that is often genetic or more rarely that appeared during your development: either your face lacks forward projection or a part only is recessed (malocclusion: your upper and lower teeth don’t perfectly fit).
The only way to definitively cure it is to go through an orthognatic surgery. If not treated it might evolves into sleep apnea as you are getting older. You should check with an orthodontist or a maxillo-facial surgeon to make sure that’s what your are suffering from.
If your are lucky like me, ie you have enough projection and no malocclusion, a genioplasty might be sufficient to naturally seal your lips without muscle contraction by bringing them closer. In my case it’s what created the pressure differential needed for my tongue to stay in the roof of my mouth. If you are unlucky a BSSO, a Lefort I or both (Bimax) might be necessary. Some extreme cases might even require the three surgeries.
