The study the OP is citing indicates that prolonged standing--thus being on your feet the whole day, such as what would be required for a waiter--increases risk of cardiac events.
The key word is prolonged.
The best posture is one that constantly changing.
Thus, don't stay in one position--be it sitting or standing--for hours at a time. I sit, stand and walk throughout the workday.
The human body is meant to move, shift and change, not remain in any one fixed position.
Wills.