How can I make changes to "people" page?
Easiest way to do this:
enable Administration Views, this would provide you with a view for "/people" page. 


  Replaces administrative overview/listing pages with actual views for
  superior usability. Filter users by name, ban/blocked status, or user
  roles.


Use a filter setting boolean field to "true" or expose this filter to allow admins to filter people by "true" or "false"