This just means you're using NAT, if you don't want to remote connect to your lab, or host services there such as a server, then you can leave it enabled as it does give you some level of protection as you don't have a real IP to expose.
As for the DNS, no this wont help you here. If your router has DHCP settings it might let you configure the DNS server that it tells your network to use, the setting you're looking at is for the router device itself (or both if it's not changeable in the DHCP settings).
If the router doesn't give you enough control, you can do this per PC:
1) Click edit DNS server assignment in the Ethernet settings:

2) Select manual:

3) Turn on IPv4:

Don't worry about IPv6, its highly doubtful your ISP provides this, AU is very backwards with IPv6 support still.