It is not only a reverse proxy (which is actually just traefik), see this blog post https://pangolin.net/blog/posts/1-15-0-release

Pangolin is a hub-and-spoke style network. They actually have some comparisons between Netbird and Pangolin https://pangolin.net/blog/posts/pangolin-v-netbird and Pangolin and Tailscale https://pangolin.net/blog/posts/pangolin-v-tailscale