Looks interesting.
I think there are other similar projects, or maybe I am wrong?
What is total supply of RSK ?
Maybe, but I'm pretty sure RSK is the biggest out there!
RSK is the name of the network, RBTC is the gas, I'll assume you're talking about RBTC which is pegged 1:1 to Bitcoin, so total supply is exactly 21 million tokens, exactly like bitcoin

If RSK is the biggest out there, why is their thread not gaining attention from crypto users here?
As you noticed, so many projects have attempted to beat bitcoin or eth platform, yet the pedestal is still with bitcoin.
Though this project is claiming to be smarter than bitcoin, but how many active crypto users actually know this project?
When I mean the biggest I kinda mean the most popular, the intention behind RSK is not just to compete with bitcoin or ethereum, that's a bit too simple. This is taken from their telegram channel:
"RSKs long-term goal is to give users the ability to consume its decentralized services from any smart contract enabled blockchain, like Ethereum, EOS, and Cardano, etc."
While at the same time acting as a second layer / side chain to bitcoin, empowering the bitcoin blockchain. Also if you google Bitcoin Smartcontract RSK is on the top results.