I read that you go to connections, choose network mode- IPv4 only.
Under Local IPv4, the options are: {5fDA- etc...} , intel ethernet connection, wireguard tunnel.

Is it wireguard tunnel? In protonvpn, it shows it is using wireguard.

Intel ethernet connection is your LAN card. That's how you reach your ISP internet with the real IP.
Wireguard tunnel is a virtual adapter used for VPNs if its the only other choice there then this is it. Your general understanding is right.

General advice: toggle your VPN connection on and off and see which network connection changes its status / IP.