<?php $records = array();

    if ($results = $db->query("SELECT * FROM user_settings UNION SELECT * FROM leaderboards")) {
        if ($results->num_rows) {
    while ($row = $results->fetch_object()) {
        $records[] = $row;
    }
    $results->free();
        }
    }

      ?>
    <?php foreach ($records as $data) { ?>

...the HTML etc...

<?php } ?>

if ($results = $db->query("SELECT * FROM user_settings, leaderboards")) {