Here is my take on KOPS: it happens to work on most bikes, if they are of conventional road race bike geometry from the era when the rule was invented, but that is just coincidence, as a goal or aim it is totally invalid. As proof, look as recumbent bicycles, including the streamlined ones on which cycling speed records are set. The riders' knees are nowhere over the pedal spindle, but their knees aren't blowing up. The important thing, in my view, is the angle between your torso and your upper leg in the power part of your stroke. If that angle is too large, then you are only using your quadriceps, you can't use your glutes. Example: a beach cruiser bike with swept back bars, where you sit bolt upright. If the angle is too small, then your knees hammer your ribs and/or your hip flexibility is challenged.

So if your shoulders are very low (i.e. torso is nearly horizontal) all the time, like on a TT bike, then the saddle should be further forward, relative to the pedals, to avoid too small an angle. If your shoulders are high, like if you are riding on the bar tops or hoods with the bar level with the saddle, then the saddle should be further rearward relative to the pedals, to avoid too large an angle.

I've never tried to measure the exact desired angle, I imagine some have, but it surely varies between riders. It is more of a feeling thing, does my butt (glute) feel like it is helping out?. That is the biggest muscle group in your body, bigger than the quads, so you don't want to waste it.