4 wire fans

It's a brushless DC motor with one of the position sensors fed to the pulse output, and the PWM input switching the stator supply on and off.

Given the way that air-flow determines torque in blowers, side by side is probably near the worst circumstance.

If you want exact same they will probably response to some sort of PLL if you want near same some sort of charge-pump feedback

If you want closely matched fans - quadcopter drones do that using multiple motor controllers.

I.e., it's a 3-wire fan with power fed through a switching element AT the fan, controlled by a low voltage signal from <wherever>. You can't expect ANY sort of performance from it, as an individual sample.

I have no idea how they will be positioned -- nor how many will be deployed. The above was intended to identify that they would be in near identical operating conditions. I need to know what I can expect from a fan before I can sort out how to use it.

Cooling fans seem to have considerably longer expected lifespans ("tens of thousands" of hours of operation vs. "a few thousand" for those of a drone). And, I don't have to worry about "packaging it" in a form that is safe for humans to approach.

I'll site a little MCU at each fan and command them appropriately. Then, let each report on faults it experiences as well as the "work being done" -- as an indicator/predictor of failure, dirty filters, obstructions, etc. (i.e., need for intervention). I.e., all those comms being relatively low frequency activities.