Removing grub-customizer from your system won’t remove it’s config-files which will heavily interfere with the “normal” grub-configs in /etc/grub.d/. So you will have to restore the original ones manually, which can be tricky. If not doing this, after the next grub-update, your system is fairly likely to be unbootable.
See the OP, and your subfolder named /etc/grub.d/proxifiedScripts/ for the original files, but be aware that grub-customizer has renamed these files. If wanting to restore them, you have to use the file-names from the original folder in /etc/grub.d/ .