You can publish multiple gardens from the same Roam Graph by using different "public markers".
Public marker is the tag you use to mark page as public (make-public by default).
If you choose one tag at one time and another tag at another time when publishing things - different sets of pages (having corresponding tags) would be published.
This garden and my main garden (at https://vlad.roam.garden/) are based on the same database for example. This garden is using Help Garden as a marker and main garden is using make-public