Your build looks good (setting the ongoing intel issues that somebody else already mentioned aside), but personally I’d consider a different drive than the Samsung - it’s a great drive, but usually overpriced imo. If you can get it for a good price then absolutely go for it, but most times I find sn850x drives significantly cheaper and insignificantly slower. Otherwise, the only other note I’d make is that grub is abysmally slow at higher resolutions on chips with no igpu, at least when using a nvidia gpu. I’m not certain if this would apply to an AMD gpu, and either way you can just use something better (cough cough refind) to avoid the problem, but for anyone who just wants the default out-of-the-box bootloader on most distros to just work properly it might be worth spending the extra ~$40 for the K series instead of the KF to get the igpu. It’s not something I’d recommend doing personally, but it’s at least worthwhile to know about when you’re making the K/KF choice imo. Anyway, good luck with your build and have fun with setting everything up!

I did a search for nvidia on my system and got these, which OP might wanna check for too:

egl-wayland
lib32-nvidia-utils
libvdpau
libxnvctrl
nvidia-open
nvidia-settings
nvidia-utils
opencl-nvidia 

I’ve installed extra packages for proton and machine learning, so some of these may not be there, but hopefully that helps.

Well your /efi entry looks right to me - maybe try mount -a (maybe capital A, going off memory here but whichever option is all) and watch for error messages or check dmesg?

sdb looks like the bootable USB to me - /dev/sda1 should be the system’s EFI, no? OP, could you try mounting that one (shouldn’t be encrypted afaik) and/or post the output of cat /etc/fstab? Edit: just realized you were unable to mount the encrypted drive in the first place so /etc is inaccessible, sorry