First of all, I would question whether you really need that much power on the axis drives. Seriously. You should experiment a bit with one axis and a load.
Secondly, do not try to compare modern digital CNC systems with those from (say) 30+ years ago. The older designs were a rats nest of technologies, every one different.
1: Different SW packages handle closed loop in different ways. Modern digital CNCs tend towards either open loop steppers or closed loop (ie encoder) servo motors.
With steppers, you just have to 'calibrate' your machine parameters: peak velocity and peak acceleration. Stay within those limits and you should be OK.
With encoder-controlled servo systems, the motor driver handles the 'closed loop' bit. If all is well, then all is well. If the motor lags too far the driver senses this and flags the controller with a fault. The system stops. You do not need the controller itself to handle the closing of the loop.
2: Modern CNCs are digital. They do not use analog control; they use digital controls. And that falls neatly into the Step/Dir paradigm. The controller does the mapping, and tells the motor driver to go 100 steps that-away. If you are moving 2 (or more) axes together, the controller handles the synchronisation.
3: see above.
You have a good range of servo motors to call on. Brushed DC motors, BrushLess DC motors, AC servo motors, and probably more.
Cheers
Roger