The system seems to be stable now, but it doesn't look like the Quick Sync feature of the iGPU is working, at least not in Final Cut Pro X. Here are a few stats for a 1080p 30fps video with 7 minutes 30 seconds long.
Hackintosh with GTX 980 Ti: 7min 50secs
Hackintosh with iGPU: 7min 27secs
MacBook Pro (early 2013): 2min 50secs
The specs on MacBook can be found here:
https://support.apple.com/kb/sp669?locale=en_US
I got the 2.7GHz quad-core, 16GB of 1600MHz DDR3L onboard memory
As you can see the iGPU doesn't really seem to help and quick sync not being used on my Hackintosh. Even for a CPU only render, 7min seems like a long time to export a 7min 1080p 30 fps video. Even Premiere is faster than that.
iStat Menus 5 showed 50% of CPU being used both for the Hackintosh and the MacBook Pro.
ABOUT THE CSM
I then switched the CSM to Disabled, and I got my monitors to work while they are plugged into my 980. But then I checked About This Mac, and I saw the 980 being used instead of the iGPU. So I went back into the BIOS and enabled the CSM again. My 1440p monitor was plugged into the motherboard, while my 1080p monitor was plugged into the 980. This time, for some strange reason, the Hackintosh showed up on both of my monitors AND showing the iGPU being used when I checked About This Mac.
BUT after a few minutes, my 1440p monitor went black again, just like the other times I have mentioned in this thread. But for some reason, my 1080p monitor which is on the 980, still works. So it doesn't seem like the system is rebooting like I previously thought, it's only the 1440p monitor going black. There is one way to make the 1440p monitor work again and that's if I use "Mirror Displays" from the 1080p monitor. As soon as I turn the mirror off, my 1440p monitor goes black again. So it only works with mirror displays on.
So that's my latest update. 1440p monitor going black, and the iGPU not using quick sync for Final Cut.