Hello! Yes the three-display config is wonderful for Media Composer editing, and growing fast in popularity. Left display is bins and project stuff. Right display is timeline only. A third display is mounted above the right display and shows Composer window, color tools, etc. Very cool.
I have seen this done in the way you described. The only major issue you might run into is an Apple issue, not an Avid one. In Catalina… I think 10.15.6 if I remember correctly… Apple users in all industries not just media saw 2nd-display and 3rd-display issues introduced. (Some Apple users said it was only seen in a specific couple of video card configs, but I never saw that mentioned publicly.) It was still there in early BigSur versions too, much to everyone’s dismay. it affected iMacs, it affected older iMacs being used in Target Display Mode, as well as laptops.
As of BigSur 11.5.x series, I no longer hear anyone complaining about it so it must’ve been fixed or at least patched by Apple. Unsure. So if you get the gear, plug it all in, and discover something is not working, you might want to consider updating your OS. Just a heads-up.