I am seeing very slow DNS resolution on Lich (US) while Haedus and Iklil are solid and quick. I am using Wireguard in Eddie 2.21.6. The server page for Lich shows nothing amiss so not sure.
10.4.0.1 is reachable from all subnets in the VPN network. So it's a reliable address. In fact, I've been using static 10.4.0.1 for some years now and for 1.5 years I've been connecting to different ports as well (which affects the subnet).