The Mac (every model) runs its fans in a feedback loop, based on measured temperatures inside at several different places.
What you are suggesting to do should be unnecessary, because the Mac generally takes care of running the fans faster when it measures higher temperatures.
No one has the information you seek, because the Mac takes care of it itself. The voltage for each fan is adjusted until the fan speed, as seen by the fan's RPM output, is appropriate for the temperatures measured.
If you wish to fiddle with it anyway, programs that call themselves "fan control" can place a new floor under the minimum fan speeds. They should NOT be able to reduce fan speeds from the defaults, as that would allow your computer to overheat. So in that way they are not truly fan control.