You can see Stratis presentation in Coinstop Melbourne. A nice presentation, not very long to find out what Stratis is.
Bitcoin Gold is a new fork of Bitcoin. To claim you have to import private keys to a Bitcoin Gold wallet. Beware of scam wallets. Importing a private key to a scam wallet, you can lose your BTC and BTG too. It is safe to move your Bitcoins to another wallet with different Bitcoin addresses, so in case of a scam wallet, the corresponding Bitcoin address has zero Bitcoins.