Kind of. It depends on the router/firewall. If you have a router that does hairpin NAT and sees traffic destined for the WAN IP and intercepts to keep it all on the LAN then effectively there is no difference. If your router can not do hairpin then you'll see the traffic actually go out the WAN interface and try to come back in the WAN interface.
A quick and dirty check that doesn't cover all the bases is to run a traceroute to the WAN IP and see what intermediary hops it passes through.
But in the end a remote check like ShieldsUP will show what ports are seen as open from the internet at large.