Oops - my mistake. I was thinking of mWh, which is a unit of energy. The total stored energy is the same regardless of how the batteries are hooked together, but that’s not true for mAh.
From experience with small electric model aircraft, I’d say NiMHs will have no difficulty putting out the current to run a laptop. A plane can run a set of NiMHs flat in under ten minutes without killing them (tho’ they may get good and hot at multi-amp current draw). And if you want to search around a bit, you should be able to get higher capacity AAs if you happen to want higher capacity - there are some about the place that are well into the 2200-2300 mAh range.
And if you multiply the stored current by the voltage, you get stored energy.
Let’s say you had a battery with a stored current of 1 amp-second at 1 volt. 1 A·s = 1 J/s·V x 1 s = 1 J/V; 1 J/V x 1 V = 1 J. Therefore, it stores 1 joule of energy.