Those are typically a variable push, variable speed belt setup. The 14 speeds are just graduated pedal travel limits.
The higher the "speed" the farther the pedal can be depressed, the faster you go.
Assuming all is working as it should, the tension on the pedal is regulated by a pedal return spring and
a spring on a takeup pulley on the final drive belt .
I suppose those springs might be replaceable with lighter tension units, but I do not know if that is advisable.
Good luck.