Using one Sanity studio for different documents on primary and subdomains.

Can I use one sanity studio and use specific documents for my primary domain and different specific documents for a subdomain? (or would I need the enterprise feature, where I can change between different datasets?)

If I understand correctly, if they are different documents in both instances you can use Workspaces: https://www.sanity.io/docs/workspaces which kind of acts like two elements in the config, which creates a kind of dropdown in the studio to pivot between them.
Enterprise would come into play if the
two datasets needed to make references between each other .

Awesome! Thank you so much

No problem!