Set up VNC to use iPad Pro with Apple Pencil as a graphics tablet
I’m slightly expecting you’ll find this workable since AstroPad and Luna display are the best solution I know for your specific use case, but I’ll presume you have reasons to discard them as solutions. 


https://lunadisplay.com/
https://astropad.com/


(Everyone else, use the tools above if you can, the tools below are the best screen share and tablet apps as well, so I highly recommend all these links)

The tool I use for Mac Remote Desktop is screens app and you can use your phone or a second iPad as a touch device or use the pencil in touch mode as you request. 


https://apps.apple.com/us/app/screens/id655890150


Been using screens for years, and only my full time artist colleagues use the accelerated versions, but they love the custom tools when they cant just render on iPad directly which is the case more and more. Screens is way better than the other “vnc” apps due to this feature and a few others IMO. 

Also, check out touchpad if you don’t need to see the content VNC on the iPad, that is even more responsive than the above solutions. 


https://apps.apple.com/us/app/touchpad/id297623931