First, a reel produces no power. You do. The reels is a transmission. It "transmits" power, supplied by you, to whatever is at the end of your line. So the most common statement made, in this context, is buy a lower ratio reel because it has more power. Nonsense.
you said "define power". OK, power is work over time. One horsepower = 33000 ft/lbs per minutes. Move 33000 pounds one foot, in one minute, and you have used one horsepower.
Another way to look at it; if the force increases, the distance and time remain the same, horsepower is increased. If force and distance remain the same and speed decreases, power is reduced.
To make this relate to the topic at hand, consider this. When you reel in a crank bait you are supplying power to move a bait a certain distance. The force part of the equation is the resistance of the bait plus some friction. That force applied over the distance is the work. Factor in the time it takes to get it all the way back, and you get the power required.
if you retrieve the same bait the same distance in the same time, the required power output power from the reel is the same. Gear ratio has nothing to do with it.
Now, let us look at input power; the part you supply by turning your crank. Using the same bait, moving the same distance, at the same speed. When using a 4:1 ratio reel, you will turn the crank X number of times. Using an 8:1 ratio reel you will turn the crank X/2 times, half as many revolutions. Each revolution requires you to move your hand a certain distance. The force required to turn the crank will be different. The 8:1 reel will require twice the force of the 4:1 reel. The 4:1 reel will move the bait half as far as the 8:1 reel.
So, twice as many turns at half the force, versus half as much force at twice the turns, gives you an identical amount of work.
The last piece of this puzzle, is then the speed. If you move the bait at the exact same speed with both reels, the power required is identical.
Now, stop obsessing over it, use whatever reel you have, and go fish.