Hope I did cause to much confusion with Nordvpn DNS.

Question #2) back up your settings

In LuCi go to system pull down tab and click Backup / Firmware upgrade. Under the heading backup and restore there is a button that says generate achieve click it and save it to your harddrive. This is a backup of all your settings. to use it click browse next to restore backup find you file and click upload.

Question #3) Turn off ad guard VPN

I’m not sure I understand correctly, There are times when AdGaurd Home block something that is needed to use a website, is what I think you are getting at. You can add a rule to the Filter DNS allowlist.

If you want to be able to have one computer not use VPN then use the VPN policy located secound from the bottom of the GL-iNet GUI. You can have it exclude vpn use for certain Ip/domains or MAC addresses. You can not have both it is either one or the other.

I have mine set up to exclude Certain MAC addresses from the vpn use. It will still use adguard Home for DNS quires