Really wish ppl would do the research before repeating what the Rumor Mill spits out. So far rubix_1011 is the only one to actually hit the nail on the head.
The whole 'noise' debate started @ 20 years ago with the founding of Noctua. At that time, and still today, they produce some of the quietest fans for pc's. Then in @ 2009 Noctua released its flagship, and things went spastic. You had Big Air NH-D14, the king of aircoolers and the Corsair H100. The H100 had craptastic noisebeasts for fans, hitting 2400rpm. The NH-D14 barely tweaking an uber silent 1000rpm.
Air coolers are quieter than AIO's! Well of course that was true, you had the 2 most popular coolers on the market, one was air and silent, the other liquid and jet engine replicating.
And the rumor mill has not stopped since, regardless of the fact that more often than not liquid coolers are far quieter than many air coolers. But to compare the noise output of any Noctua heatsink to any AIO, that's just patently unfair. I'd put my NZXT Kraken X61 up against my Cryorig R1 Ultimate any day of the week and twice on Sunday and the AIO wins hands down in EVERY competition.
It's all in the fan, the capacity, the load. Small heat exchanger, crappy fan, high load = noisy.
I have that case, the nCase M1 v6.1. It's tiny. But Very good. Still trying to source parts for my 2x 240mm radiator custom loop.

That's my size 10 sneaker box. There's a 1" difference