Hyperexcitability does not improve cognition. It usually does the opposite: it raises background noise, lowers the signal-to-noise ratio, and makes information processing less stable.
In migraine, this is why increased neural firing is not a sign of better mental performance. The same state that makes trigeminal nociceptors easier to activate also makes attention, memory, and processing speed less reliable, especially during an attack or in central sensitisation.
Any apparent link between migraine and creativity is indirect. It may reflect sensitivity, divergent association, or unusual perception, but not improved cognitive function.
More excitation is not the same as better thought.