Thanks for your question, I only have experience on the constant speed, variable pitch installation as fitted to the Lockheed P3 Orion.
In very simple terms:
The jet engine rotates at 13,820rpm all the time (best torque and econ rpm), with the propellor rotating at 1021rmp, all the time.
The prop control is a electronically controlled, hyraulically actuated system.
I'll stick to the inflight control system, as the system does change slightly for ground ops, (including a lower rpm setting)
From the cockpit, the FE sees rpm variations of only =/- 1% as power changes are made, because the prop control will sense any variations in prop rpm, as more fuel is added or removed from the engine fuel supply by movement of the power levers by the pilot.
For instance, if the power levers are advanced, more fuel is introduced into the engine, the prop control senses the prop starting to incr. rpm, and will immediately incr. the blade angle to absorb that energy, and thus increasing thrust, almost immediately, since no actual incr. in rpm is required.
Inside the prop control, there are three hyd. pumps, two are driven mechanically, by the actual turning of the prop, and the third is driven electically, for altering the prop blade angle when the prop is not turning.
The predominant 'dome' in the centre of the prop, contains one very large hyd. piston, with a transverse tube down the centre.
This piston is connected mechanically to all the prop blades, thereby controlling the blade angle of each.
The prop control also contains an rpm sensor, which directs hyd. pressure to move the blades to incr. or decr. the blade angle to maintain the prop at exactly 100%
There is a thing called 'ATM' or Aerodynamic Turning Moment, which tries to decr. the blade angle always, as it turns and produces lift, so effectively, the piston is only holding the blades against this effect, except, of course when very large blade angle changes are called for, when the piston will drive as required.
Also, when sudden power lever changes are commanded, the prop syncronization system has a function where it will anticipate the incoming fuelflow change (+ or -), and actually start to incr. or decr. the blade angle (in anticipation), to limit the amount of rpm swing during these turbulent times.
When the prop is feathered inflt., as the prop rpm decreases rapidly, thereby severly reducing the effective output of the two mech. pumps, the electric pump cuts in and completes the blade movement to the full 86.65 deg blade angle. very slightly to far for perfect aerodynamic feathering, and tries to drive the prop backwards, thereby mech locking the prop brake, so no prop rotation for the remainder of the flight.
This is a VERY simplified, very short explanation of a very complicated, very good system, that works very well.
I hope I covered what you were looking for,
Cheers.