If i have my content types in a hub (different site collection) and I want to use document IDs on a subscriber site, does the Document ID feature need to be active on both the hub and the subscriber?
The Document ID Service feature is enabled at the site collection level. Whether or not that site collection consumes content types from a hub is irrelevant. The document ID will get a prefix unique to the site collection (which can be changed).
When the Document ID Service feature is enabled, the document ID column will be added to all documents created in the site.