As Danr sys - yes. Flywheels are nice but not necessary for model locomotives. Some complain about "sudden stops" with non-flywheel locos, but I have never really had this problem. The old Pullmors never had flywheels, either; they had different dynamics and no traction tires, I know, but still.
The tachometer-type speed control - like PS2 - usually uses a flywheel for the tach tape, etc. ERR does not.