Mine is a Laing DDC, and it's clearly not the same, but it shares some characteristics: 100% speed is around 60-65% PWM, among other things. I never run it even close to those speeds - at idle I run it at 20%/1200rpm, which is perfectly adequate for desktop use, and under load it ramps up to a peak of 45%/3400rpm, at which point it provides plenty of flow and is still essentially inaudible.
It's worth noting that noise does not increase linearly with pump speed with my DDC, and I had to test a bunch of speeds to find the most quiet ones, then tune its curve to hit those spots and not just ramp willy-nilly. For example, 2800-3000rpm are far noisier than 3400; 2000-2200 is pretty bad as well, while the mid-2000s are okay - but 3400 is no louder, and performs better.
Edit: it's also worth noting that with a noise source with a bit of mass, like a water pump, resonances are your worst enemy, and that's why running through the frequency spectrum to find the least resonant areas is worth doing. What resonates and how will vary depending not only on the pump and how it vibrates, but on pretty much all the hardware in your build, from the water block/pump mount to the case, AICs, motherboard, other components, the tightness of screws, production tolerances for various components, etc.
