So the reason for 140mm fans on a 120mm radiator is cost. Currently nf-f12 ippc(120mm fan) sells for around 2(two) to 3(three) times as much around $50 to $75 on Amazon and eBay currently for the 3000 rpm model. $25 for the nf-a14 ippc (140mm fan) 3000 rpm model. So if nf-a14 would work I would prefer that.
Noctua IPPC? Oh, please no, don't do that. I've been there already - ran with a bunch of NF-F12s and NF-A14s for a little over a year, to sate my curiosity and for experimental reasons.
They are a waste of money in a home PC. Server fans, ventilation fan for mining rigs/farms located away from you and others, sure - you know, for
Industrial applications as Noctua states.
Those fans are amazing(power), don't get me wrong, but if you don't actually USE that extra 1000-1500rpm, then they are wasted on you.
I was curious to see what they offered over the normal fans, as well as how loud they got - those Youtube videos don't do them any justice!
They do not improve overall thermals by much, considering you get a jet sitting next to you...
I used them to find a slightly higher overclock; I succeeded, but once I did, I found myself using that extra horsepower less and less.
Now, I have these 3000rpm IPPC fans that I run like they were the regular Noctuas because I no longer have a purpose or reason to run them like that anymore - that, and the noise(at max rpm) was finally starting to bother me.