The legs are important as they provide the bulk of the power. If the base is not stable, then the rest of the swing will fall out of tune.
Balance is maintained basically within the legs so they are important to the overall swing.
I've got those happy feet, those low-down snappy feet, and I feel like dancing. The back foot should remain planted, and rotate on the balls of the feet to perform a pivot. This is to maintain balance throughout the swing. Both legs should remain bent to ease adjustment and avoid stiffness.