Appears to cost 2 extra buzz (matching type used for generator) regardless of model type (Illustrious and Nanobanana both take only 2 extra). Yes, ad for memberships is still there, undismissable, and stays there when working with models that don't allow that kind of content.
(Also the tooltip style for model statistics like DLs changed a few days ago, but I didn't mention it because it's not really a functional change.)