Nvidia Inspector cli with parameter -setFanSpeed:0,80 ( 1st value is the number of the card 0,1,2,3... , second value is the fixed fan speed in percentage ) , you can use also -setTempTarget:0,0,70 , -setPowerTarget:0,70 if its working for your purpose.

example : nvidiaInspector.exe -setFanSpeed:0,80 -setFanSpeed:1,80 -setFanSpeed:2,80

This do the same as set fixed fan speed in MSI Afterburner , as for fan curve there is no such functionality for now.