There's been several issues in the past with mismatched GPU's in scenarios like this. Mileage will vary. If you already have the cards, it wouldn't hurt to try, but I wouldn't suggest going out and buying a new setup like this without testing first.
Yeah with 40 some PJ's, if you want them to mosaic a single raster. That's getting a bit advanced lol.
$$ and budget start going out the window at that point.
SMPTE 2110 has a sync protocol built in, so maybe going down that rabbit hole might be a way to get signal to and from, but that equipment isn't cheap and you need a massive transport backbone to get signal to end point devices. a single 4k stream exceeds a 10Gbps pipeline. And you would need to find a program that could take in a massive raster and slice it up and out to SMPTE 2110 (I don't know of any)
