I’d also be curious about this. Say for the use case of running a small private chat server hosted on a home network; does either of these seem better suited, or are they just different architectures that can handle mostly similar things?
YG puts more "magic" on protocol (autorouting, mesh making, etc), but is not that clean on design (crypto not formally tested, latency prone TCP links, not good enough NAT punching, etc).
Wireguard and YG are different tools on the SDN network toolbox, and can be mixed for special porpoises.