Thank you for the advice. I found putting the insert on the top layer and on that applying the effect to be counter-intuitive. The terms ‘foreground’ and ‘background’ are a bit misleading. ‘Insert’ would be more precise and consistent.
I ended up using mocha Pro in AMC. Starting with the background plate, added mocha Pro, tracked the shot, then created one of the screen inserts. Into that I imported the .mov file, rather than use the layer below as insert. I then copied that clip to a lower layer, and repeated the insert with a different monitor. With up to 13 layers of mocha, my system ground to a halt. So I did some video mixdowns to simplify the processing. Once the screens are created, I place a clean layer of the BG plate on top and key it with Primatte.
This worked until I upgraded to mocha Pro 2020. My imported .mov insert screens went black. Upon opening up in the effect editor / mocha interface, there was an error message about the media being corrupt (I reported this error in the mocha Pro forum). Downgrading to 2019.5 restored the video imports.
I am only doing these as temps to get the producer to sign off on the design of the screens. Ultimately, a professional will actually make these shots.
BTW, I’ve looked at every mocha Pro tutorial I can find on the Boris site, Youtube, Vimeo. Although extremely helpful, it takes time for me, an editor, to absorb the concepts (tracking, insert layer, surface tool, grid tool) and how they work together. At times I track a shot, create an insert, then get wildy off results. It baffles me when the surface moves differently from the insert shape.
The hardest part, I think, is understanding how to correctly track a shot. Most of the shots in the demos are relatively straightforward. The shots I encounter seem much more complicated. Shots that are handheld, with two people walk through the frame, at times completely blocking the frame and surface I’m tracking. Or a green card with no tracking marks that should be a photograph, but is variously blocked, curled and moved, making it seemingly impossible to track.
I love the challenge, though. And greatly appreciate the feedback and support from BorisFx.