2x AdGuard Home: what/where to put IPv4/6 DNS addresses?

I've installed Adguard Home on my Banana R3 (OpenWrt) and in a docker container on my NAS (Asustor AS6704T). It is working but quite often quite slow. My assumption is that I did not state the IP addresses of the 2 AdGuard Home instances correctly for IPv6 on one or more places.
Banana R3 OpenWrt =
Docker container on NAS =

Current config:

Network - DHCP and DNS - Forward:

System - Interfaces - wan:

System - Interfaces - lan - Advanced Settings:

System - Interfaces - lan - DHCP Server - Advanced Settings - DHCP Options:

System - Interfaces - lan - DHCP Server - IPv6 Settings:

Is there something I can correct/improve?
What am I supposed to state as IPv6 DNS servers for and
Do I have to give some IPv6 DHCP options?
Should DNS serves explicitly be stated in lan interface?

Thanks in advance for your help.