The bit that annoys me always (and what makes Ah a meaningless measurement for power banks) is whether the amp-hours rating is just the internal batteries' spec summed together, or is it as measured at the 5V outlet? Huge difference!

I would assume it’s whichever gives the highest number which is usually going to be the internal voltage.

For instance I have a 20000mAh power bank which also has a 74Wh capacity printed on, a conversion factor of 3.7V matching li-ion chemistry.

Not to mention with PD neither the neither input not output voltages are limited to 5V.