Airtable has a built in CreatedBy field.  It sounds like this is what you are trying todo.  Then when an record is update happens you have LastModifiedBy

I also initially expected that the “user who took action” for a “when record created” trigger would be the user who created the record, but it currently is not. 

As far as I can tell, the “user who took action” only knows about users who push interface buttons that trigger automation and users who edit field values. 

Thank you, I would have thought that value was the one I needed, so I just backed into be solution from a different angle now knowing this!