Need help on a DC motor-PWM-SMPS setup (Does a PWM help overcome a DC motor's initial startup current surge?)
This PWM appears to be a good choice as it has an unspecified SOFT START.

This means the duty cycle must start from 0 to the pot set value for some reasonable preset time such as >0.1 second by design assumptions for small motor start time.

Motors have an inductive where current rises with dI/dt = V/L so if dt starts at 0  then the soft start PWM ought to eliminate the or reduce the 10x start surge significantly.   Normally the start surge is due to the full voltage integrated to reach V+/Rs the coil resistance. But with a "soft-start" or ramped PWM duty cycle to set level by Pot, the average voltage starts low and the pump starts slow.  I would expect this soft period to be at least 100ms but preferably >1s with only 10% of the starting current to avoid full power start of 10x rated current.

If the Soft-start was done right for motors, with this 100W/12V = 8.2A motor a 15A PWM soft-start could work but I see it has a 30A rating which will run cooler.