Trouble Booting Into UEFI BIOS

Hi All, I have a noob question that I'm hoping you can help me with.
I recently built a dual boot system using two separate 1TB Samsung 860 Evo SSDs. Windows 10 Pro is installed on one SSD, while Catalina is installed on the other. I used the OpenCore vanilla guide to get my hackintosh up and running.

MOBO: ASUS ROG STRIX MINI ITX
CPU: Intel I7 9700K

Here's my problem:
I cannot boot into my BIOS with either of my drives attached. I can boot into the windows or hackintosh drive using the opencore bootloader, but I can only access the bios if both SSDs are unplugged. If even a single SSD is plugged in and I mash F2/DEL on startup, I get a black screen plus the green error LED on the motherboard indicating a "BOOT" issue.

This wasn't always a problem. Back when I first installed Catalina on my SSD, I could still boot into the BIOS, but every time I shut down Catalina my computer would forcibly restart into BIOS Safe Mode. I disabled this using:
Kernel -> Quirks -> DisableRtcChecksum -> true
And I believe this is where my error is coming from.

Additional info:
When I first changed DisableRtcChecksum to true, I was not able to boot into the BIOS with the mac drive plugged in, but I could if the mac drive was unplugged and the windows drive was plugged in. I'm not sure when I stopped being able to boot into the BIOS with only the windows drive plugged in.

It would be ideal if my computer forcibly booted into the BIOS every time (but not BIOS Safe Mode) and forced me to select which drive to boot off of. I don't like how opencore gives me a limited time to select my boot drive, plus it's kind of annoying to read that tiny menu on my 4k monitor. But I'd also be happy with a solution that just allows me to boot from one drive to the other and into BIOS freely without having to unplug something every time.

Apologies if this is question has been answered somewhere. In my research I was not able to find a solution to my problem. Any explanation is appreciated, as it's important to me that I understand what is going on. Thank you in advance.