I did more testing.
At 12bits of resolution at 300Hz it changes speed from from a min 1400 to 2500, 34 to 61% PWM.
The servo class has a resolution of 180. This had a resolution of ~1100. I published the values to ThingSpeak, you can see changed about every other one, even with magnets doubling the weight of the propeller. So I’d want at least 500+ values of resolution to control a quadcopter using ESCs.
https://thingspeak.com/channels/201525
Note measuring propeller speed should be done optically, but I had a hall sensor already hooked up. I’ll find the magnet that flew off eventually.