Earlier quoted context omitted.
My water cooler is noisy at the fan end. How do you evade that?
If your fans are noisy buy better fans. We had some corsair fans that came with the AIO at work, replaced them with noctuas and the computer went from mildly annoying to dead silent. Though with water cooling you might also have a lot of pump noise, especially if the radiator is mounted incorrectly.
The larger the diameter of a fan, the lower the RPM it can spin at to move the same amount of air (same cooling capacity) as a small fan. Provided you can put the air where it's needed (e.g. a 1 foot fan can't "focus" air onto a 6 inch radiator) a larger fan will just about always be quieter and more efficient.
Oh, and having a water cooled PC with the radiator and fan inside the PC itself is silly. If you run the pipes outside or into your basement, your PC is almost completely silent, plus the cooling capacity will usually be much, much higher, because not having to cram fans and a radiator into a small enclosure lets you make them bigger and more efficient.