AP One-Name Studies follows the Guild of One-Name Studies definitions exactly.

• A variant is a spelling actually used - by the person, or consistently in records - and is registered under the study surname.
• A deviant is a one-off error (a typo, misreading or mishearing). It is held on record so its entries stay findable, without joining the surname's spelling family.

Manage both on the Spellings tab. Removing a spelling from the study leaves occurrences already tagged with it unchanged - they keep their tag.