Graphics Cards

[txupport]

So, I have attempted my best google-fu to try and find a solution, but only managed to come up with solutions that were either irrelevant to my situation or something that was ineffective as a whole.

I have a 3 monitor setup with the center showing as 3
I want to set the center screen as 1, so when I use Win+P to select "PC screen only" it will use the center screen, instead of what happens as shown here - I have the center set with "make this my main display" and have tried booting with just the center attached and it starts as 1, but as soon as I connect either of the other monitors it changes to 2/3.
GPU is a RX 580 8G, center screen is HDMI, the side monitors are DP, if that helps at all.
The whole issue driving me to inquire about this is that I have a noticeable drop in performance when I run a game while the other displays are connected, mostly a 10-15% FPS drop and some hanging.
Any help is greatly appreciated, thanks in advance.