Since most of web handling revolves around rollers (pardon the pun), the logical way to create tension is to control torque transmitted to the shafts of unwinders, winders, and rollers. Rotary brakes and clutches are torque controlling devices. Many motors can also be operated in a torque control mode.
The tension (in force per width, such at N/m or lbs/in) created by an applied torque is equal to the torque (in N-m or lbs-in) divided by the web width (in m or in) and the radial distance (in m or in) from the web to the axis of rotation. For a given winder or unwinder torque, the tension is inversely proportional to roll radius.
Braked or clutches rollers are less common. Torque applied to a roller will attempt to create a torque differential, assuming the frictional force at the web to roller contact is high enough to avoid slippage.