Who are block producers and how things work in Rainbowbridge?
The same validators who are validators for Ethereum or NEAR - are the one who produce blocks.
There is no special BPs, for the Rainbow Bridge: it is just a bunch of smart contracts working together.
You can read more about how Rainbow Bridge works here:
https://aurora.dev/blog/2021-how-the-rainbow-bridge-works
To host your own RPC node you will need to use this repo: