You've listed the PV input maximum, but not the ideal.
To keep your array below the maximum, while maximizing your input voltage you'd do one string of 16, which gives you a maximum voltage of 720V, and a nominal voltage of 600V.
This is probably right about where your pump wants to be, so will probably be your best configuration.
If your pump, however, has a high range but prefers a lower voltage, then two parallel strings of nine panels each might work best. That gives a maximum voltage of 405V, and a nominal voltage of 338v.
Make sure, however, that you understand your needs. If the panels are on a tracker, and on a sunny day, they would produce 5.4kW, but if they are fixed mount, pointing south, then you'll get peaks near 5kW for an hour or two on bright days, and you'll get 1-2kW in the morning and afternoon, with peaks around 3kW on many days.
That will affect your head pressure and volume, and if you're designing near the pump's limit, then you won't see any pumping for most of the day. The pump will be spinning, but it won't be generating its rated output unless the VFD is providing its rated input - and it simply won't be most of the day, even on sunny days, unless you have more panels or a solar tracking unit.
The solar VFD does not have energy storage, so all it can do is give as much power to the pump as it's receiving in solar at that moment.
