Helical swimmers, actuated by low-strength uniform rotating magnetic fields, can develop swimming and pumping in low Reynolds number environments. They could play an important role for future in vitro and in vivo biomedical microrobotic tasks. Studying how their morphology influences swimming and pumping tasks is then of importance. In this paper, we focus on two geometrical aspects for optimizing both tasks: their helical shape and their cross-section. As a first contribution, we investigate the optimal performance of swimming and pumping. As a second contribution, we elucidate between optimal shapes at performing swimming and pumping at the same time. This study based on numerical simulation is intended to serve as a guiding reference for building optimal helical structures either for swimming, pumping, or a combination of both tasks.