Rob here, if I understand you are wishing to use a graphic tablet - why not buy a Wacom … tablet and plug this into a laptop etc and your have something that works. If you are maybe thinking plug iPad into a laptop and draw using astopad why would you do this ?
Maybe the program on the laptop and you can mirror to the iPad using astro pad ?
If it helps any I use Skype on a laptop and share screen to the iPad and listen to the questions and draw the answers out to my students.
Since zoom came into play I just draw using the iPad and share the screen, it appears to work fine with paid version.
My preferred method is plug a Wacom tablet into a desktop and share screen this way, CPU takes a hit. When you wifi astro pad to say a laptop and too slow in response for myself.
Router is as fast as I can get and LAN as fast as it can get.
Maybe give us all a visual experience of what you do now as my answer may not even touch the surface.
Bottom line Astropad built more for using P-shop and have it appear on your iPad - un paid version has many restrictions - sorry subscription has many restrictions like you cannot rotate screen …
Hence you might be better off with a dedicated drawing tablet that is designed to work with a desktop
hope that helps ?