Yeah I figured that; I’ve got a 2070 Super tho and only owned it since November 2019 and hasn’t had much use on it really other than gaming...temps look all fine and once it’s running it’s perfectly fine it literally is on first boot when monitor turns on for the first time like it’s adjusting and finding the signal....it’s only started since BIOS update so it’s very confusing!
Im not sure as if you are having the display issues to may be similar? Also my OS is on an M2 so not HDD used unless it’s for games or storage
Your SSD can be either MBR or GPT. Most likely it is GPT so it is UEFI Mode in BIOS.
If your SSD was MBR Partitioned it wouldn't boot if BIOS is in UEFI Mode. It would need to be in CSM Mode to boot.
But Asus CSM Mode is compatible with both MBR and GPT Partitions.
In my case, my HDD is GPT and in Windows it says it is UEFI Mode compatible even though I have it set for CSM Mode in BIOS.
Note: I have a Nvidia GTX1070 GPU card.