I don’t use Netbird, but at first glance they don’t seem to gave a mobile client yet? This means it’s limited to desktop usage right now. Otherwise, it’s built on Wireguard, which is the same with Tailscale. The only difference being the maturity of each project, Tailscale being the more mature one.

Headscale is the open source Tailscale login server that you can self-host, by the way.