All those books definitely talk to some degree about those areas. I forget which ones, but they say the anatomy of the maxilla (the upper jawbone which forms the nose) is key to breathing. And dentists talk about a "constricted arch" which I think is a related issue. I don't think I have these issues so I didn't pay particular attention there.

The way I think about it is that breathing is a big geometry problem, and everyone is a little different, and every medical provider has their own viewpoint, and set of solutions they can apply. For example I don't think Nestor has the same problems that I have. He talks about his problems in the YouTube video and in the book.

So you will probably have to look around a lot. It's a big topic. But the common point is that almost all humans have problems breathing, but it manifests in different ways depending on the unique geometry of their head.

It's kind of like if you crushed 100 pumpkins, not all of them are going to be crushed in the same way, but they'll all have some problem ...

And it depends on medical history -- a lot of people seem to have bad breathing because of childhood orthodontic work.

e.g. I found this person through Google:

https://www.righttogrow.org/mf_s_story

When I was a young girl I had orthodontic extractions and wore a cervical headgear that pulled my upper jaw back and made my oral cavity much smaller than nature intended it to be. Before this treatment, I was a fit and healthy child who had no problems sleeping and waking up. After extractions and headgear, part of my vitality went away and I lived a life of constant fatigue, plagued with fainting spells and low energy for more than twenty years

Feel free to reach out by e-mail if you learn anything interesting about your case!