I had a similar experience, with a slightly different approach (mouth tape and a nose dilator) but seemingly similar outcome. I like that you did it just through exercises with no mechanical intervention. Inspiring.
I’ve found this is all really worth learning, even if you don’t have sleep apnea. I feel more clear headed and energized when I can breath through my nose now.
Regardless, it doesn't cost anything to try, seems no danger in it and it seems logical that it could help.
Can you elaborate more on this? I also assume by "mewing" you mean putting the tip of your tongue on your hard palette right behind your upper incisor, and letting the rest of the tongue suction against the hard (and soft) palette. Surprisingly for something that seems to be so "popular" in "broscience" I find it hard to find any canonical definition or technique.