How can I mask out the region in a video where there is a human, such that I get 2 layers, 1 for the human and the other where there is background
Without a greenscreen your other option would be to hand rotoscope in After Effects. There’s no clean, simple, and fast way currently to reliably get a mask for a moving person other than some distinction with the background (green/bluescreen being the most common) There are AI options making progress but not plugin.