This should list out anyone who has made personal configurations to their Overview page - it shows you what portlets they have on their page (which may or may not be the same as the system defined layout of the Overview page!).
SELECT
(SELECT user_name || ' / ' || last_name || ', ' || first_name FROM cmn_sec_users u WHERE u.ID = p.principal_id ) Who
,(select portlet_code from cmn_portlets pt where pt.id = p.portlet_id ) Portlet
FROM
cmn_page_portlets p
WHERE principal_type = 'USER'
AND page_id = ( select id from cmn_pages pg where pg.page_code = 'npt.overview' )
(obviously you can just change the various filters in that query to pick up other pages etc)