Closed-loop tension control requires tension feedback by either a transducer or dancer roller. If you control tension without a transducer roller (a.k.a. load cell or tension roller) or a dancer roller, then you are using open-loop tension control. Torque control and draw control, without tension feedback, are both open-loop tension control methods.
If your control brake torque applied to the shaft of an unwinding roll, you can increase or decrease the web tension by adjusting the brake torque. Similarly, using a torque-limiting clutch control on a winding shaft will create tension, but is not closed-loop control without tension feedback.
Both unwinding or winding torque control systems need to change torque proportional to roll diameter to maintain constant tension. An advanced torque control system will include a diameter sensor to automatically adjust the torque proportional to roll diameter, coming close to constant tension control, but without tension feedback, they are still open-loop tension control.
The greatest weakness of an open-loop torque system is inertial torque. Web tension is proportional to the resisting torque divided by the roll or roller radius. For steady speeds, a diameter-based torque compensation system will do a reasonable job in creating uniform tension; however, during acceleration and decelerations, the roll or roller mass will add or subtract from the applied clutch or brake torque, creating a significant uncompensated tension variation.