Ive only had to setup a nvidia system once, so I might be missing some packages, but I think pacman -Rns nvidia nvidia-utils lib32-nvidia-utils should get rid of all of it.

WARNING: doing this will absolutely DESTROY YOUR SYSTEM, PERMANENTLY!!!

But if you wish to continue, you can erase all the EFI variables using the rm utility, I dont think you will be able to completely zero out the chip on the system from inside of Linux as its read-only.

But to delete all the EFI variables, cd into /sys/firmware/efi/efivars, if this directory is not availiable, either the efivarfs is not mounted, or you are booted in legacy BIOS mode. But once you are in this directory, run chattr -i ./* as root or sudo to remove the immutable bit on all the files, then run rm ./* as root. This WILL break your system. Only do this if you know how to restore your system using like a chip programmer.

This happened to me too. I had to grab the box that comes up and resize it like I would with a normal window, mine glitched a lot when I tried it, try resizing it as far as you can, it will try and glitch back, but just keep fighting it until it becomes a usable size, then log out of Plasma and log back in, and then you can size it back down to a normal size. Hopefully there will be an official fix for this soon