RT-AX86U Pro DNS-Server-settings-a-go-go

[Steve23]

I've been using the RT-AX86U Pro with the beta firmware for several months, primarily testing its VLAN features but also other useful features such as VPN Fusion, etc.

Recently I began looking more closely at the various DNS Server settings and feeling more than a little doubt that I know what they all meant. A (hopefully) quick rundown...

In my LAN settings, the DNS Server settings are empty.

Spoiler: Fig 1: LAN DNS settings

Fig 1. Advanced Settings>LAN>LAN-DHCP Server>DNS & WINS Server Setting

Then there's the WAN DNS server settings. I have mine set not to connect automatically, rather to use the IPs entered. These are the Quad9 servers many of us use.

Spoiler: Fig 2: WAN DNS Settings

Fig 2. Adv settings>WAN>Internet Connection>Edit PVC>WAN DNS Setting

Then the RT-AX86U Pro beta firmware adds VLANs with - you guessed it - DNS Settings fields!

Spoiler: Fig 3 & 4: VLAN DNS Settings

Fig 3. VLAN DNS Set to connect automatically (green slider at lower right).

Fig 4. VLAN DNS set to NOT connect automatically.

This brings me to the questions I have, probably asked a million times in one form or another...

1) Looking at Fig 3, when this is set to connect automatically, does this then refer back to the info in the WAN DNS settings?

2) My WAN DNS settings currently say NOT to connect automatically so I presume it would use the Quad9 servers, correct?

3) Looking at Fig 4, when I set the VLAN DNS setting to NOT connect automatically, I can either "assign" or use the "default." What's "default?" Is that, once again, referring back to the WAN DNS settings?

4) If I click "assign" it becomes possible (presumably) to choose a different DNS server than the WAN DNS settings or the same ones. Does it matter if this is redundant in that way (if I were to choose the same Quad9 servers)?

Thanks for indulging me!