Salesforce has cascade delete functionality. When you create the entity, make sure the entity includes both parent and child tables if the child tables have cascade delete set to true. Otherwise, in the Delete from Source step of the purge job or archive and purge job, Salesforce deletes the child records automatically while deleting the parent records.

When you select the

Include Salesforce Archived Records

check box in the source connection, the driver gets the records that are archived by Salesforce in addition to the soft-deleted records. If you use the same connection to archive data from any custom entities, it is your responsibility to filter out the soft-deleted records by appending "IsDeleted=false" in the entity's select, insert and delete query.