What does "WAN DNS Setting" do?

[Crimliar]

Are any of the DNS security features necessary and do they slow down gaming traffic?

Thanks

DNS queries just look up an address - they just give you where you want to go, they don't tell you how to get there. So the data between you and the game server you are connecting to NEVER passes through the DNS server. Instead, the packets of data you send over the internet get the address you retrieved from the DNS server stuck on the front of them, and that address is used by routing servers (the equivalent of sort centres for physical goods sent through the mail) to get your data to its destination.