This site is being deprecated.
Please see the official X‑Plane Support page for help.
I am not with Laminar Research; just a flight simmer.
Firstly unless there has been a dramatic change with XP 11.30, X-Plane does not run in SLI mode. So you need to disconnect that system.
Secondly as you have a top of the range graphics card run all screens from the single most powerful card you have. Connect the screens to the Display Ports on your card and the HDMI ports on your screens.
Configure your screens within X-Plane and not through your operating system or using GSync. Read the manual which can be found at https://x-plane.com/manuals/desktop/#configuringamulti-monitorsimulator
Also have a look at the video listing from Russ Barlow which can be found at https://www.youtube.com/user/srbarlow/videos In particular have a look at videos dealing with multiple screens produced about 2 years ago and the last video to view was produced about 12 months ago.
This site is no longer being actively maintained.