Here is kind of how I define things and sometimes I use these terms interchangeably, sometimes this is appropriate and sometimes it is not as you will see.
Power Endurance (PE) is the ability to produce a certain power output for a given period of time.
Power Capacity (PC) is essentially the maximum sustainable power one can produce for a given volume of work.
So lets do a little mathematics here.
PE = Power x Time or F(d/t)(t) so it’s really just total amount of work or Work Capacity. This is why I believe Power-Endurance and Work Capacity can go hand in hand, but focusing on the power aspects of improving work capacity is of greater benefit to an athlete.
PC = Power x Work is really the square of work divided time {(F x d)(f x d)/t }, but should calculated as P x PE were P is absolute maximal power output. This mathematically is considered a rate just like power is a rate. This is useful in expressing the ability to do a given amount of work at a given rate, but its most useful aspect is identifying if someone can increase power or increase work in a work capacity (PE) workout or not. Someone with a higher power capacity should be able to do work at a higher rate (power) than someone who has a lower power capacity. That same person should have the ability to do more work at a given rate than someone who has lower power capacity thus the prolonged duration aspect which is helpful to endurance athletes.
Given the presented information, Work Capacity is limited by Power Capacity and the ability to endure a given power output ie.. Power-Endurance. In what should be a trade-off of both power and endurance as one should suffer at the hand of the other, we can find there is not this trade off unless we work above approximately 85% 1RM or below approximately 75% 1RM. The adaptations should benefit both pure power output and the ability to endure. The best part is this seems to translate well to the weight room, multi-jumps, multi-throws, and on the track. As 85% 1RM is about 3-6 reps in the weight room and 75% 1RM is about 8-12 1RM depending on the individual and most individuals perform anywhere between 3-8 reps in standard weight room activities. 80-85% is approximately the intensity of a special/speed endurance rep on the track, while 75-80% is a tempo/special endurance rep on the track when relating it to maximum intensity.