I think you misunderstand how mesh VPNs work. Their primary purpose is as a control plane - introducing peers to each other so they can either communicate directly or via a relay (eg DERP) via per-node encryption. They should have no overhead compared to a single point to point encrypted tunnel like wireguard, because the “mesh” features are not in the data path.

The only real difference here is how the vpn product implements wireguard: userspace or kernel space, and how well tuned that implementation is. It might make sense to compare wireguard implementations, but (afaik) all are using one of several open source ones. Tailscale did some work to improve performance that they blogged about here https://tailscale.com/blog/more-throughput