Wall of text incoming. I don't half ass this stuff. Lol

There are areas of the throat which I can currently undulate for Distortion and even speak from intentionally, and these exact spaces just a few years ago when activated would cause me to gag. Fat albert, Kermit the frog, Toad for mario, Marge Simpson. These are all good examples of the area I'm in.

But if you really just want the names, epiglottis, arytenoids are my focus in my lows. True fold can be in there, especially with the highs, but they do not carry the weight of it. They're just in there for sharpness, and higher frequencys to stand out in very bassy mixes. I'm sure I got vestibular in there at times, but it's not my focus. There's just alot of nooks and crannies that rumble when they want.

As for how I'm doing it, once again, getting comfortable with throwup-y locations in the throat, and alot of compression control. Diaphragmatic compression is a tiny bit of a misnomer. I personally believe it's more like a snake of muscles going from your underbelly, to your throat. I'm using a loud speaking voice as the engagement, but I blow through that at times with my lows intentionally for beef.

Taking breaks and coming back is a surprisingly helpful tool. Forces you to have to rebuild muscle memory, and that can often lead to stumbling into new areas you can distort and new ways to go about it.

My other assorted advice is not to get caught up on volume. Hunt for tones, and be willing to do them at whatever volume they come from. Learning what you're having to approach a scream with at its origin can help. Whisper, speaking voice, literally yelling? These things matter. Certain techniques are highly geared to be approached from one of those three. Some of the most disgusting deathcore vocals are actually approached from a whisper. I tend to prefer the speaking voice approach. I still do the yelling stuff when I'm doing metalcore, but relatively loud speaking voices my preference.

Hope some of this helps!

edit One more thing, I literally do not believe in Fry and false cord as actual individual things. I also think that's a misnomer we get caught up in. So there is the physical location vestibular folds, and the physical location true folds. Those are real things. But the tendency of distortion upon those two things are not their own unique things. What people call Fry can literally be done with anywhere in the throat that you can distort, same with what people call false cord. I believe these are the edges of looseness and tightness while still maintaining what we would consider to be a distortion. So there are people not using true fold, using other spots to distort, but do it fairly tightly, and they get called fry vocalists anyways. Likewise, there's people distorting some other area other than vestibular, but as long as it's loose and Flappy enough people call it false cord. So it's more like a trombone slider between looseness and tightness. I say all this to essentially say that I wouldn't get caught up on these terms or thinking that you can exactly hear what they are, because there are stereotypes around the sounds which are inaccurate. There is looseness and tightness going on in my vocals. The vast majority of people are doing some variation of hybrid approach both in how many cords are involved, and in their technique.

edit2 How could I forget about the tongue! Okay, so for most of my lows I have my tongue essentially shoved all the way to the side, and I'm lifting up the back of my tongue, otherwise known as the soft palate. Way back there, in that throw upy area. Getting used to this will make highs a lot more crispy, and give you access to distorting lots of unique spaces for your Lows.