Optimizing negative hydrogen ion sources (NHISs) remains a critical challenge for neutral beam injection (NBI) systems in tokamak fusion facilities. However, the high experimental cost and the spatial limitations of low-dimensional simulations for multiple-driver NHISs highlight the need to perform high-dimensional simulations. In this paper, a 3D fluid plasma model is employed to compare the performance of multiple-driver ion sources in two magnetic filter field configurations: the permanent magnet (PM) configuration and the plasma grid current (IPG) configuration. For double-driver ion sources, the PM configuration outperforms the IPG configuration in terms of uniformity parallel to the magnetic field. The IPG return conductor design critically governs the magnetic filter field topology. Therefore, this study also systematically investigates how the position and quantity of the return conductor affect plasma parameters. Simulations demonstrate that positioning conductors inside the expansion region increases the electron density, H density, and volume-generated H− density near the extraction region versus back-plate placement. Moving the conductors towards the plasma grid (PG) or increasing the conductor number further enhances their densities significantly. For quadruple-driver ion sources, the IPG configuration offers better uniformity parallel to the magnetic field than the PM configuration, making it the preferred choice. The variation in values of plasma parameters for various conductor positions and quantities is similar to that observed in double-driver ion sources. Moreover, increased conductor numbers also improve plasma parameter uniformity perpendicular to the magnetic field in quadruple-driver ion sources.