How similar is the "Open Device" mechanism for Screen sharing and Control similar to VNC Server mechanism like Veency? Could the client iOS be used directly using a VNC Client over USB just as AS connects to it?

How similar is the “Open Device” mechanism for Screen sharing and Control similar to VNC Server mechanism like Veency? Could the client iOS be used directly using a VNC Client over USB just as AS connects to it?

I do not think it is possible since VNC needs some interface to talk or instruct commands to iOS device screen share and control.

It is already doing that. I am guessing AS using a VNC like / some screen & control mechanism here. Does it not?

Not for control. May be for screen share. I think for control some other mechanism is used.