I did many, many air cooled variations in ncase.
The best cooler i've ever used in that case was discontinued NH-C14 from Noctua, which run my i7 8700k at 23-25 degrees idle.
NH U9S is a great alternative, it's not discontinued, you don't have any problems fitting cables or rams with this cooler, but it runs hotter by 6-7 degrees than c14 does. At least that's what my tests showed. Getting NH-c14 inside was pain in the arse, since that cooler completely hides sata ports, usb header port.. and if you want to take system apart, then you literally have to take everything one by one. So unless you find cheap NH c14 and have skills to install without ruining something then you're good. Otherwise u9s is the easiest solution in terms of everything. I literally sold my Ncase because i scratched it too much and started disliking it. I might order a new one some time later, but dunno yet.
Also I found it really hard to fit AIO shield in my Ncase, the one from asrock just kept popping in. Other cases used to clamp them down, but mine just felt like squashed and not proportional.