The Hedera previewnet supports developers using all of Hedera's network services — it will be the first to support any up-and-coming services, as well.
The network services on the Hedera previewnet are throttled: https://docs.hedera.com/guides/testnet#network-throttles
The Hedera developer quick-start guide can be found here: https://docs.hedera.com/guides/getting-started/introduction