Welcome Alex! Good to see you here. I think you'll do well!
It's definitely still worth posting on both platforms.

Dan Larimer and Ned Scott started the Steem blockchain as well as Steemit.com.
D.Tube was created by Hive account@heimindanger

The videos are stored on IPFS ( https://ipfs.io/ )

Checkout this interview with Hive account@ned and Hive account@heimindanger discussing the future of Steemit and D.Tube recorded a couple days ago:

Videos exploring the differences between the entrenched centralized platforms an the emerging decentralized versions are interesting and highly relevant. Keep it up!