The elements vary a bit, mostly by name. For the YMK Hapkido folks the principles are "The Water Principle", "Point and Circle Principle" and "Economy of Energy".
As far as the other bits there are usually a more varied approach in labels but the dynamics are simliar. For instance, every meaningful Hapkido art touches on "taking balance", "misaligning the attacker", disrupting the attackers' timing or focus, and so forth. The method for accomplishing these things often varies with the art, or even with the priorities of the teacher. FWIW.
Best Wishes,
Bruce