A Twitch public relay can be shared with 100s of other people all fighting over bandwidth. A private relay is in its own "Container" so your relay is not shared with anyone else, bandwidth is also carefully controlled so every container has its amount.
Yes, but we do not advise sharing private relays with many people as this defeats the whole point of a private relay.
Yes, If you have Linux experience you can easily set this up within SSH, We can also do this for you at an additional charge.
We utilize Proxmox LXC for private relay servers.