Are we still using only 256 unique PWM steps?

[EricVanWyk]

Even an LT3080 would go vapor phase / light on fire / explode if used for this. Simply put, linear regulators are not used to drive motors. You should look up "H-Bridge" for some good explanations of how motor controllers work.

I'm still not convinced that you would actually see any benefit from additional resolution. The issue is resolution vs accuracy. In your 30RPM vs 4000 RPM example you have less than 1% error from resolution, but the accuracy is going to be many times that error from sources. For example, a good battery's rest voltage will vary several volts over the course of a match, and the actual voltage seen will swing wildly during normal transient loads. Open loop, any extra resolution in the bridge's duty cycle will be worthless.

To compensate, wrap a PID loop around an encoder on the wheel. This will help with the accuracy error sources, and will eventually oscillate around a few values as it tries to dial in the speed. It will never be perfect, but it should be good enough.