I understand now.... I thought you might have discovered how to change things for one fan at a time, to individually tune them. Rather, you are changing all via the BIOS at once, and thus having all be Noctua fans makes sense for this experiment.
This will be interesting.... I'm looking forward to seeing where you use those each and how you mount them. I see you have 4 that are bigger than stock, the one 92mm fan, and then also that nice little one.