For the user redirection part you will have it setup like this:
link in the menu goes to clients_results.php. On this page you have an access rule to restrict access to only directors. For the redirect page you will specify the page that you crafted for admins to see theirs and other clients.
On this clients page you will have an access check to ensure that the user is an admin. If they fail this check then you will want to redirect them to the client clients_results_user.php.
If a use is not a director or admin they will click on this link and be denied on this page, this will send the user to the admin view page, they will fail this check and be sent to the user version of the page.
For filtering the recordset you will need to do it like your last idea, choose filter the foreign key clientuserid = session variable userid.