There are getters and setters for the options. We don't remove them but we set them to appropriate values depending upon requirement and type of option.
For example if we want to remove row grouping our code would be
$grid.pqGrid( "option" , "groupModel", null ); //setter
$grid.pqGrid( "refreshDataAndView" );
and if we want to add one more field to existing row grouping, our code would be
var GM = $grid.pqGrid( "option" , "groupModel");//getter
GM.dataIndx.push( dataIndx );
GM.dir.push( "up" );
$grid.pqGrid( "option" , "groupModel", GM);//setter