PWM or Pulse Width Modulation has generally been regarded as too complicated for PC fan speed control compared against using rheostats or linear voltage regulators such as the LM317.

NesteQ MaxZero 8-Channel Fan Controller / Temperature Monitor While the plugs on the controller are all 3 prong (I believe), they come with the PWM 4-prong adapters.

Of course, you can also skip the PWM code and just use the timer interrupts for timing. It isn’t that the timer code or PWM isn’t workable without a tool.