@Fatboi, might be helpful to start with the basics / first princples.

First, for every amount of power that you can put out in watts, there is a duration over which you can sustain it. And although the difference is likely imperceptible if youâ€™re talking single-difference in power, really the max duration for each power level is different. If you can hold 1000 watts for 5 seconds, then you can hold 500 watts for longer. And then if you have an Y axis that is power and an X axis that is duration, and put each of these maximum efforts on the graph and draw a line through them, you get a curve, called the Power-Duration Curve. The PDC is not what you can sustain over the course of one effort, rather each point represents a different effort.

Second, every single personâ€™s PDC is different. Certain things will always be true about them (such as duration goes down as power goes up), and theyâ€™ll likely be somewhat similar because of physiology, but each one is different.

Third, 4DP is like a â€śsimplifiedâ€ť PDC. Itâ€™d be great to test every conceivable duration but itâ€™s not practical and would get you diminishing returns. So 4DP picks a couple of durations based on certain known physiological touch points based on how your body creates energy to do the effort. But they make you test each oneâ€“rather than just having a test that estimates FTP and then doing the rest by %â€“because as per above, each personâ€™s PDC is different.

Then on to FTP: FTP is supposed to be an estimate of Maximal Lactate Steady State (MLSS), which is the highest work load (in watts in our case) that can be maintained over time without a continued blood lactate accumulation. It implies some anaerobic contribution but a small enough amount that you can keep using the lactate for fuel and it doesnâ€™t build up. You can think about it as like, the hardest â€śhardâ€ť effort that you can sustain for an appreciable period of time, OR you can think about it as like, the effort level below which you can sustain for longer than an hour, but above which you fatigue non-linearly more quickly.

So â€śFTPâ€ť basically means an estimate of MLSS that you obtained by doing a power test (i.e., a â€śfunctionalâ€ť test). One way of estimating it is one-hour power (although note your MLSSw may or may not be sustainable for precisely one hour), Sufferfest 4DP is another way of estimating FTP.

Putting it together, youâ€™re basically asking, what power (expressed in relation to FTP) should i be climbing at, and it should be clear that just like @Alistair_Brown said, there is no one single right answer. It depends on the length of the climb (power/duration), how fast youâ€™re trying to go, and how many times you need to repeat it. If each climb is short (4 mins) and youâ€™re doing a one hour ride and trying to really crush it, maybe you can climb around MAP. If youâ€™re doing a ride that will take 8 hours and has 9000 feet of elevation gain, you will likely get your fastest time by climbing below FTP, starting conservative and trying to negative split it.