John,
1.) PWM does not reduce the drive torque. (see recent thread) And you can servo speed easily.
2.) Back-emf sensing works with ANY DC drive. You are sensing the generation of volts across the armature as the armature spins in a magnetic field.

As I said, there are many methods of doing it. F. Stephen Venables showed an elegant design in a recent EDN if I remember correctly.

Best wishes

Steve