How much can Core i7 13645HX's performance change between power modes, and when should performance mode be used?

  The 13645HX, like all HX chips, ties performance mode to a higher power ceiling and louder fans. Sustained heavy loads (rendering, encoding, AAA) gain clearly; light loads gain nothing.

  Practical rule: plugged in and pushing hard, use performance mode; office work on balanced; unplugged and needing battery, quiet mode. Every chassis schedules power differently, so run one task yourself in both modes for the most accurate comparison.