Comparing LXD vs. LXC

now, i am curious. with a few containers, or more. can i build a multi-node multi-LAN -like network and do some complex routing, like maybe with OSPF?

Depends on what you had in mind. I am using ospf inside some containers provided by frr. The containers are attached to multiple vlans, which I have created with openvswitch on the host. Works nicely even across openvpn tunnels.