Hi Owen,
You are right, current-institution-affiliation-name includes all affiliations that have no end date or that end date is in the future.
past-institution-affiliation-name includes all affiliations with an end date that is in the past.
If the affiliation doesn't have dates at all, it will be included in the current-institution-affiliation-name .
Regarding the given-and-family-names field, you are also right, it is only a search value and will not be included in the results.
Thanks