Update from this post from the other day: What to know before Dual Booting Windows + Linux?

TLDR: I got it working, started learning, tried to fix a grub issue and borked the whole system.

So after considering all the advice, I went and disabled/prepped/backed up, and started the process. I managed to get Fedora KDE installed on another partition and everything was looking ok. I installed some programs, started learning for a few hours, but there was one small issue. The grub configuration from the video didn't really work. Windows wasn't booting by default, and when I tried to do the GRUB_SAVEDEFAULT=true to have it boot the last OS, it also didn't work. When booting windows, a message would flash by saying '/EFI/fedora/grubenv' not found.

Looking more into it, the video says to use sudo grub2-mkconfig -o boot/efi/EFI/fedora/grub.cfg but I think the correct one now is grub2-mkconfig -o /boot/grub2/grub.cfg? I found this thread, but I couldn't run the first command because it gave a conflict error, and I think there were two versions of grub2 installed?

So anyways, I tried running the setup again, thought it was ok and did a reboot to test... and got hit with a black screen with minimal BASH like line editing is supported.

At this point I'm a little worried and lost, thinking maybe I wasn't ready to try this, and trying to get it back the way it was. I found this guide, but I get stuck trying to mount the EFI partition.

Any tips on where to go from here? Right now I plugged in the USB I used earlier, booted Fedora from it, and opened the terminal. Past that I'm a bit lost on how to fix grub.