Great project.
Forget all scene capture actors, they are not meant for quality of renders you probably need. And this would eat a lot of fps.
Instead You should try multiplayer setup with each player covering 90deg (or 45).
If you can setup unreal to always target same monitor, you will be almost there.
Also with multiplayer built in from beginning you will get easy way to expand for multiple PCs.
So set up multiplayer, make player controller send exactly same input to all pawns (that control cameras).
For this create function in player controller that tells location and rotation of player, make all pawns register to it, and follow player location.
At Event BeginGame assign monitors ids and add correct local rotation to their cameras.
Then you can add some umg gui to assign each player pawn to separate (or same PC).