...some excellent points ! However I prefer not to mix anything into the final fluid combo before leak-testing. As I build both servers / workstations as well as fun machines, I have a setup with an external Molex that powers all the pumps etc for a new w-cooling build w/o having to turn the main mobo on. I let that run for several hours, power and cool down, than run for another few minutes - be that for a single loop or dual loops. More on fans below...
...I have a collection of the Noctuas - but that colour ! I use them for workstations that go into 'boxes', but for open builds, no thank you. I got so desperate on a personal TT Core P5 build that I actually spray-painted some Noctuas black (still work, btw).
...for benchers and heavy duty, I use the tried and true GentleTyphoon 4K rpm models, each w/ 183 CFM...they are for example on my GPU loop for dual 2080 Tis and they just keep everything below the first speed-bin loss...so far, I haven't been able to 'heat-soak' that GPU loop with 760 W in 2 years, and not for lack of trying !
..we also have a big pile of repatriated Sunon 5K rpm server fans, but while they certainly cool very well, they just can't be used if you sit within earshot, whereby I find the GentleTyphoons 'somewhat bearable' ? ...GT 4K on the left, Sunon 5K on the right:
...lately however, I have been getting into Arctic P12 pwm PST fans - and I'm genuinely shocked at the great price-temp_noise performance ratio, especially if you buy the 5 value pack. Obviously I don't know yet how reliable they are over the longer term, but they sure beat the cr_p out of for example Corsair ML 120s, both in terms of noise at full tilt, and temps w/ all other factors held equal.
I just put 5 of those into 'The Thing' (you know as the Strix 3090 OC testbench) - 3 for the CPU, and 2 for the GPU backplate (double-sided GDDR6X = toasty). When I watercool the Strix, I'll be using those. The question is whether they last as long as for example the GentleTyphoons (some of those are over 8 years old, & in continuous use...).