OK thanks for getting back to me,
The active Dual Link adapters, can I use the apple one that is bus powered? Or should I get something that has an actual AC adapter to it?

I am not as concerned about real time clock as it is just loops for an install, I just need to make sure all 3 screens are in sync as they will form a vertical panorama so to speak. Sync IDs should be fine internally I would hope.

In your experience, in terms of performance load on the machine, does it make more sense to play back 1 x 4k file and just split it up with offsets in the mix windows or play back 4 x 1080? I have never been able to actually try this side by side and see yet, just curious

I think just because I want to use less layers I will do 1 x 4k and split it up....