Axe, not contradicting anything that anybody on here is saying (as i`m just getting back into this).

What i will say though is in relation to your display problem there really ought not to be any problems in disconnecting the cables.
I have 2off sapphire rx580 nitro + cards in my new rig and I only had display cables connected to them during setup.
The cards have never had video cables connected to them after that as i just use the mobo (AS Rock H110 Pro BTC+) video out.
I know this doesn`t solve your prob, but it does let you know that disconnecting the cables shouldn`t have any affect.
FWIW i`m running the current claymore miner on zec.

Actually on second read of your post i note that your cards are 4GB where as mine are 8GB.
Wouldn`t think this would make any difference, but someone else may be able to advise.

Hope you get fixed up.