Q) How to apply more advanced conditional formatting?

You can set onload event in PHP code, and enable 'reloadedit' option

    // set js onload event
    $e["js_on_load_complete"] = "grid_onload";
    $g->set_events($e);

    // required to format rows after editing
    $opt["reloadedit"] = true;
    ...
    $g->set_options($opt);

Then in HTML code, you can have custom conditional logic in javascript handler.
In this code, list1 is grid id. You can also use php's equivalent '$g->id' to reference it.

    <script>
    function grid_onload(ids)
    {
        if(ids.rows)
            jQuery.each(ids.rows,function(i)
            {
                // if col1 = yes and col2 = n/a, format row
                if (this.col1.toLowerCase() == 'yes' && this.col2.toLowerCase() == 'n/a')
                {
                    // highlight row
                    jQuery('#list1 tr.jqgrow:eq('+i+')').css('background-image','inherit').css({'background-color':'#FBEC88', 'color':'red'});
                }

                // if col3 = 1, format cell. 'aria-describedby=list1_col3' is 'gridid_colname' convention to identify cell.
                if (parseInt(this.col3) == 1)
                {
                    // highlight cell
                    jQuery('#list1 tr.jqgrow:eq('+i+')').css('background-image','inherit');
                    jQuery('#list1 tr.jqgrow:eq('+i+') td[aria-describedby=list1_col3]').css('background','inherit').css({'background-color':'#FBEC88', 'color':'red'});
                }
            });
    }
    </script>