API - Getting owner information of a file that is not shared

Its not an issue, but I was looking for the right/best way to find users/groups that has access to a list of files. 

Below are the steps:

a.  The list of files (fileIds) in a Business Account (with Teamspace config) is fetched first using list_folder/list_folder_continue APIs. The authenticating user is Admin for the business account. The list includes private (non shared) files as well belonging different members in the account.

b.  Now, with each of these fileIds, I was trying to fetch sharing info with the sharing/list_file_members API.  I was able to get details for all files in team/shared folders with this. 

c.  As sharing info was not available for private files, I was looking at Metadata for "owner" information, however thats not directly available in Metadata or sharing info. 

I followed what Greg-DB suggested, and below are the 3 cases depending on the file ownership/sharing status

1.   For files in shared/team folders -> sharing/list_file_members API gives the information. No issues here.

2.  For files that are private and belonging to members other than authenticated user  -> sharing/list_file_members API gives sharing info -> and from that, modified by field gives the account Id. With the account id, I am getting account info and finding the team member id (owner)

3.  For files that are private and belonging to current authenticated user (in my case, the admin user) -> unlike case (2) sharing info is NULL in the response to sharing/list_file_members. In this case, I already know the admin user's member Id. So, assigning that as the owner.

I am not sure if the approaches followed in (2) and (3) are the right/best way since it involves multiple API calls to get the owner/access information.