A: The AA version of the BOOST FP is rated at 2500mWh and AAA version is rated at 1000mWh.
By comparison a 2100mAh AA NiMH battery is rated at 2520mWh (1.2v x 2100mAh) so the BOOST FP AA battery contains similar power to a 2100mAh NiMH AA battery.
The useable capacity will depend on the minimum voltage required by your electronic device. It will also vary depending on the discharge rate. If your electronics requires at least 1.1v to operate, the BOOST FP is equivalent to around a 2400mAh NiMH battery. If your electronics requires at least 1.15v to operate, the BOOST FP is equivalent to around a 2600mAH to 2700mAH NiMH battery.