Wanted to add, the power limit it just that, a power limit. it does not automatically send extra power the the GPU, it simply allows it to request more power.
As you increase the clock speeds, and voltages, the card will pull more power, but with the stock bios, those increases will be very small because they do not allow you much freedom in your choice of GPU voltage.
e.g., with my GTX 760, the voltage increase is capped at a piss poor 12mv, thus at max overclock, and (1304MHz core, and 6.8GHz memory with +12mv to the GPU, the max power usage only jumps to 102% even though I have the limit set to 145%)
The only cards that manage to go more than 1-3% above the the 100% mark for the 760, are the hawx series which have a voltage control circuit which was reverse engineered a few years ago, but is still used today because it is a very robust controller. (those cards can be soft modded to allow the foll voltage range (you can crank it high enough to instantly fry the GPU if you want)