I connected my iPad Pro to my macBook to use it as a pen display for Grease Pencil (I also tried scultping, same issue). This solution has a noticable latency in general and is as of right now no substitution for a 'real' pen display. But it works and gets the intended strokes onto the canvas. So it does at least in Photoshop. In Blender I couldn't make it work. It's very laggy and the biggest issue is that it doesn't recognize all the 'points' made by the pen. So if I make fast long strokes across the screen, it either draws nothing or only a short straight line with only a start and end (wich btw are also not accurate). It looks like a very simplified version of my intended stroke.
Now I also tried the app Duet on my PC with a AMD Vega 56. It feels like it's a bit better, but still not a working solution. And still it works fine in Photoshop but is not acceptable in Blender. Small short strokes are always boiled down to very reduced length lines with few points.
Appreciate any help :) Thanks