No type2 means it's a successfully forwarded port. A FORWARDED port means traffic freely flows in both directions. This includes incoming traffic that was uninitiated by you like a regular port forward. In a port forward, all incomming traffic on that forwarded port will be destined to that forwarded client. Traffic flows in both directions and is never dropped.
Type3 means traffic flows freely in one direction with an unsolistated incomming traffic dropped. This is not port forwarded behavior, but rather what occurs every time a router does its NAT translation. This is not a network problem but just typical expected closed port behavior.
So there you have it, it's either forwarded or it's not, SIMPLE.
So what is Nat1 you may ask? It means that the console received incoming traffic on ports that it didn't yet request to have forwarded. This traffic was tested before the forward was initiated. If this traffic still reached the client, instead of being dropped (typically any NAT would drop these packets) then console assumes that NAT is not being formared or already OPEN/pointing to the console without any forward requests. Once again, the console then assumes that no Network Address Translation is taking place since traffic is reaching the client without requested forwards, which is non typical or OPEN/NAT1 behavior. This is the exact behavior that would happen if it WASN'T behind a router, aka fully open throughout the entire port range, no forwarding required.
If you want this fully open behavior, then it still is achieve this possible while behind a router. You would have to forward all the ports to your console which is exactly what the DMZ does. Now the console won't have to request ports since all of them already point to it so you have NAT1 behavior. This behavior will performed at the expense of all your other clients. Other clients won't able to request any ports since NON will be free.
Otherwise, instead of forwarding all ports with DMZ, you can permanently forward a limited range of ports to your console by using static port forwarding. This will make so the console does not have to request the ports itself. It will act like NAT1 on predefined ports. This is a pseudo NAT1 since its not open on the entire range.
Now explain to me how a NAT1 system is better than NAT2? With NAT2, the console requests what it needs and it is granted if it's available. The grant is FULL two way traffic. Gone are the days where you are stuck on NAT3 until you manually forward. The only way I see where NAT1 would be better in the situation where the console is actually pushing traffic on ports that it DID NOT request to open. This is improper behavior on the console side, should be fixed console side, and should of never been exhibited in the first place. Only work around is a static port forward for this occurance, while it is patched.
In the bigger picture you only have 1 PUBLIC ip which is why you are doing NAT in the first place. Any incomming connection on a public WAN port has to be forwarded to a single device or dropped. Port forwards do NOT drop any incoming questions. Non-port forward traffic is typically dropped if not intiated/triggered by the client in accordance to the 4 types discussed (Cone,Symettric, Etc) In reality, you CANNOT have two consoles be NAT1. The text is arbitrary
**IPV6 changes this entire scenario**
With IPV6 it is not needed to perform NAT due to the increased public addresses pool.
With IPV6 you no longer have 1 public IP, but enough to issue each device can receive a public IP.
Since all ports per IP point only to that one device, no NATting is nessecary