> Also, sometimes it seems like I get rate limited on Tailscale.

As I understand it if everything is working properly you should end up with a peer to peer wireguard connection after initial connection using tailscales infrastructure. ie, there should be nothing to rate limit. There are exceptions depending on your network environment where you need one of the relays noted in this post.

As for opensource alternatives:

https://github.com/juanfont/headscale can replace tailscales initial coordination servers

and https://netbird.io/ seemed to be a rapidly developing full stack alternative.