If the computer boots but you can’t access a GUI, use Ctrl+Alt+F3 to open a console. From there you can use nano to edit the login manager configuration. If you had GNOME installed, your login manager is probably GDM, and its config should be at /etc/gdm/daemon.conf, according to the manual. If that is the case, it looks like you should erase the username under the entry “AutomaticLogin=”.
AFAIK, the port on your router is irrelevant as the VPN bypasses it. I’m not familiar with ProtonVPN, but with PIA you can get a forwarded port in the VPN app and specify that port in your P2P application. I use that method for Soulseek, but my qBittorrent works correctly in both directions without doing anything special.
If I understand correctly, the filesystem driver is contained within the kernel for all linux-native filesystems (Ext4, XFS, BtrFS, F2FS, etc.), just as drivers for computer components and devices are. But drivers to access NTFS (Windows) and HFS+ (Mac OS) drives are programs in userspace