Is it possible to mirror iPad with sidecar window to external monitor?

for a very specific setup for a client I’m wondering if it’s possible to run sidecar on my iPad and connect the iPad to an external monitor to mirror. My end goal is to get a remote viewing monitor that I can put 15-20m away or so from main computer?

My setup would be my MBP 2017 in clamshell mode with TB3-dock and two external monitors already connected running 1200p and 1440p, both through the dock. What I’m thinking for the iPad is to be connected to what would be the third monitor (1200p) in the setup in another room with the lightning > HDMI adapter. Would this be possible? And how would it mirror it on the screen, fill top to bottom or windowed?

Unfortunately I cannot test myself as I’m stuck abroad, flying back day before the job so cannot do the testing myself before the job.

All hep appreciated!