Does increasing/integrating more panels with a lower power pump achieve a higher water output?
Any given pump has a rated capacity and maximum flow rate. As a result, increasing/integrating more solar panels as compared to the rated requirement for a particular capacity HP pump does not result in a higher water output.
However, since solar powered pumps work on the output from the solar array, increasing the number of panels in some case may increase the number of hours that the pump can operate or increase the output of water during lower levels of sunshine e.g. on a cloudy day. It is strongly recommended to consult the manufacturer/supplier to estimate the economic feasibility before making any changes.