Querybuilder Making Dynamic Query Problem

Hi I'm gonna use querybuilder to create dynamic query based on requests and have it on my resultset

                $builder = $this->modelsManager->createBuilder()
                                ->columns($columns)
                                ->from(array('ParentDB'=>'NS\Models\ParentDB'))
                                ->innerJoin('NS\Models\ChildDB','ParentDB.Id=ChildDB.parentId','ChildDB');
                if ( $condition ){
                        $builder->where( $someCondition )->getQuery()->execute( $params );
                }else{
                        $builder->getQuery()->execute();
                }

my goal is creating query dynamiclly for example join other tables if needed or add another where conditions and perhaps params.. should I use PHQL instead?