The difference between hypervigilance and hyperactivity is that in hypervigilance, it is fear-based and your body is hyperaroused, tense, and ready to fight or run from any potential danger, while in hyperactivity, it is based on disinhibition from a non-functional frontal lobe, and hence your body becomes hyperkinetic and is in constant motion due to the brain not working properly to inhibit your actions.
So hypervigilance is a fear and anxiety state that is based on hyperactive fear circuits and a hyperactive amygdala, while hyperactivity is a disinhibited state where the frontal lobes are not functioning properly to inhibit your physical actions.
So hypervigilance and hyperactivity can look similar in terms of hyperkinetic actions, but they differ as one is based on fear and survival (hyperactive amygdala), and the other on unbalanced brain control, where the brakes are not working (hypoactive frontal lobes) and it is mostly the gas pedal (accelerator).
