Just a quick test, but internally, across pure 10G links, Tailscale maxes out at 300Mbps, which is fine for things like SSH, but could definitely be better for say... mounting SMB shares.
Now, I haven't dug into why it's so slow (M4 Pro on one end, 96-core server on the other), but it may have something to do with it running in a container on TrueNAS.