For most routers, the port labels are for people and have no impact on configuration. In a layout where there isn’t a clear WAN and LAN, pick one, use both, it doesn’t matter much.

Having some connection to the LAN-labeled port is useful when doing development work or if you need to erase all settings on the router.

WireGuard is a routed tunnel, so most services can be made available. Things that require on-link packets won’t.