We just spotted a small blunder from our picture, which is also in the whitepaper. On the right side where it says "Notary nodes", but it should be "Normal nodes".

Notary nodes are elected, and there will be 64 of them. They will do the notarization to Bitcoin blockchain.

Normal nodes can be run by anyone, but because of the harder difficulty they will only find some blocks while the notary nodes will find most of them with an easier difficulty.