Cause,
I have never used acrylics much. ( Except hobby acrylics in school for a quickie class project.)
What you say about Pro-acrylics makes me think that they must have a higher pigment to binder ratio. I have see this with colored pencils. I used to use any brand of pencil, then found a better brand, then stuck with Prismacolor. More pigment, more control. But that is a different medium, and i don't mean to distract from your thread.
Holding a brush like a pencil was all I was shown to do, but again, I would not call myself an artist really. (I did try water color years ago... hated it) (tried pastels, will never try that again)
From an engineering standpoint, you need to put pigment on paper/board/canvas. If you can move up, down, left right, and control pressure and angle/twist, then you got it. If pencil holding works, then I guess your golden.
I do know this for me...if I try to draw a "perfect" circle, it comes out stretched sideways (left to right). I DO believe this to be muscle memory. Because I write cursive, print, etc...for decades... muscles and brain are "faster in that axis". So I DO hold the implement in a deliberately odd way to short circuit my brain/body program which causes the fast axis syndrome. I will hold the pencil at right angle to paper and lock wrist and use elbow, shoulder, back muscles...But that is the only time I do that (It also looks stupid). Since I use paper/pencil i can rotate paper to align straight stroke to my fast-axis and just let muscle memory fly. My art teacher in H.S. told me never to rotate paper... oh well...she also told me to never erase...

So Cause, do you find yourself thinking of EVERY stroke before its made, committing to it, and then making it. And NOT thinking when the paint stroke is being made? Or are you more relaxed and free to think while painting. I ask because, for me, when I draw, I catch myself doing the former, and I wish I could just "let it flow".
I see having a background that is not white being helpful.
My experience shows me I think in terms of adding more and more darkness. For me, its harder to see the white spaces in my minds eye. And I can't add white with my medium. So are you saying that in acrylics because you can add opaque white, or any other color, that sometimes having a different background is helpful to show where to put paint? Like if you had neutral gray background to start, would that show you where you can put light AND dark?
Sounds like you are learning a lot and having fun doing it too! And thanks for sharing, it gets me thinking about my own art, albeit a different medium.
Also... kind of curious what you know of this...
I almost always see people paint "standing up" like on an easel. I have issues with keeping blood pressure up at times. I think my arm would fall off doing that.
Does anyone paint with canvas flat down, like on a table? Seems to me you won't ever fight gravity that way too and could use really thin paint if needed...