Hi,
At this point in time, if Researcher Profiles are enabled, then the "owner" of that Researcher Profile (or any Administrator) can link/unlink it to other entities via a relationship. I'm not aware of a way to provide access restrictions on specific relationship types.
It's worth pointing out that this ability to link to other entities is required for syncing data between DSpace and ORCID.
If you turn *off* ORCID synchronization, then you don't need to have Researcher Profiles enabled either. So, you could turn those off as well. This would essentially mean that people could login via ORCID, but would not be able to sync content to/from their ORCID profile.
Tim