Delegated Proof of Stake is designed to optimize performance of the nominal condition of 100% participation of honest nodes with robust network connections. This gives DPOS the power to confirm transactions with 99.9% certainty in an average of just 1.5 seconds

63-second rounds: 21 blocks per round at a target of 3 seconds between blocks.

Bandwidth is Information carrying capacity. In Steemit It can Be Expanlied as How much information you can upload and download in a certain block of Steemit.
Bandwidth depends most on how much rewards you are getting in steem power increase your bandwidth.