Peer to peer connection using own DERP

I have several devices behind various complicated NATs. Sometimes even outbound traffic is filtered other than 80/tcp and 443/tcp.

What I can do is to install Tailscale on a VPS and open required ports that Tailscale wants, eg, 41641/udp . With this investment, will I get either peer to peer connections between all devices, or traffic between devices relayed through that VPS server (acting as a relay)?

Tailscale devices should be able to make inbound connections to that VPS server. But can they talk to each other via that server, akin to “client-to-client “ option in OpenVPN?

Another possibility is to flag a device as a DERP server in admin panel. Is this possible?


Searching internet, custom DERP seems possible