There is another problem with watercooling, which is that once the water warms up (which it will under sustained loads) your CPU temperature will begin to climb.
Then it becomes a game of "do I have thermal mass enough to run my job before throttling", and often it can be the case that radiators are unable to effectively cool down the CPU; but the additional water becomes thermal capacity; sometimes giving the appearance of better cooling when in actuality your system will throttle after 10 minutes of work.
Your heatsink is one of the better ones, an NHD-15 might be better but only slightly, after which point: I don't think it can be expected to cool a CPU at a sustained load with any AIO system, even the triple fan ones.
I'm probably not communicating this terribly well, I went down this rabbit hole when I was watercooling my old GPU and CPU in a custom loop by EK, I ended up discovering that if I wanted to do sustained work (which I did) then a direct airflow system would have worked better, so I ripped out the loop and it did work better for sustained loads.