Yes, you can do this.
I provide a packaged solution for wireguard and openvpn solutions to
make templates. - https://qubes.3isec.org/tasks.html
Whatever you do, you will need to set up the disposable template with the VPN
configuration and login, but it should work just fine.
You’ll want to make it a named disposable if you want to use it as a
VPN gateway, so you can specify it as netvm for other qubes.