Data Studio actually isn't part of GCP at all, it's part of GMP (with Analytics & DV360/DoubleClick). There are integrations between the two, but my guess is that Data Studio continues to exist in GMP and fills the role of dashboards for marketers, while Looker will fulfill the BI role.

Technically yes but datastudio is also listed as a cloud product. Datastudio actually lives in an intersection between GMP, cloud and gsuite

Yes, indeed. Lot's of connectors to non-GMP stuff:

https://datastudio.google.com/data