SOLUTION: Not a guaranteed fix for everyone, but swapping the GPU for either the 1080 Ti or the 3070 allowed me to have display to perform a BIOS update, rebooted into windows and shut down the system. Swapped to the RTX 3090 and badda bing badda boom I was past the BIOS splash screen and in Windows.
I just got my hands on an RTX 3090 Founders Edition and am stoked. But unfortunately, my system won't post and I can't seem to figure out why. The lights turn on and all my fans spin, but the motherboard Q-Code LED gets stuck on "bF" for maybe 10 seconds before shutting down. Motherboard manual isn't much help because it just says bF is "reserved for future AMI Codes" so that's not much help.
So far I have tried:
-Resetting the CMOS (reset my OC and returned CPU/RAM to stock settings, posts just fine)
-Reseating the CPU (posts just fine)
-Checking for bent/broken pins (no bent pins, posts just fine)
-Reinstalling CPU cooler to ensure proper mounting pressure (posts just fine)
-Tested all 4 RAM sticks to show they work individually, and that they work in tandem (all DIMMs work, posts just fine)
-Uninstalled my graphics card drivers
-Uninstalled my GTX 1080 Ti
-Installed the RTX 3090 FE
I'm thinking it mayyy be because my CPU lacks PCIe Gen 4.0 support, but even then it should work just fine at Gen 3.0 speeds. My system is connected to a CyberPower UPS that supports up to 1000W of power so I've confirmed the system only pulls about 135W of power when booting which is well within my power supply's limits.
Intel Core i7-6850K
Corsair H150i Pro RGB
ASUS STRIX X99 Gaming
4x8GB Corsair Vengeance RGB
RTX 3090 Founders Edition
Samsung 850 EVO 500GB
Samsung 860 EVO 1TB
Seagate Barracuda PRO 4TB
EVGA SuperNOVA 750 G2
Corsair Crystal 460X
UPDATE: I just swapped back to my GTX 1080 Ti and was able to get past the BIOS and into Windows just fine, and same thing with my buddy's RTX 3070 FE which I'm holding onto until he gets the rest of the parts for his PC. Whereas the RTX 3090 just doesn't even show the BIOS splash screen.