Brume 2 - Use as Drop-In vs Main Router

You can set up the Brume 2 as a standalone AdGuardHome server, in Router mode, without double NAT and without Drop-In Gateway.

This thread has procedures to set up a LAN-only server in Router mode and then to set up AdGuardHome to show actual client IPs.

You can also run VPN on the same LAN-only server by setting the default gateway IP of client devices to the IP of the Brume 2.