Yes, it is feasible to secure folders by employing the user's IP address as a unique identifier.
You mainly want to configure a VPN for remote access, allowing someone to join your network and then use it to reach the device.
Windows VPN might suffice depending on your needs, but external solutions like WireGuard could offer better performance and features.
It should work fine. I haven't used it before because my router already has a built-in VPN server that I rely on.