Everything looks quite *sharp* to me. There is "noise" (or at least sharpness) even on the foreground grass. So my first question, rather than about render settings, is what - if anything - you did for post processing? Any sharpening? Or did you use a "sharp" AA filter? I would definitely use higher AA than 5, too. AA8 or so for good vegetation. But if you're not using Defer Atmo (and I am not necessarily recommending that you do), then this won't improve your cloud/atmo noise. However to my eye that noise is not necessarily that obvious, or at least it might not be if the sharpening that I suspect is happening were reduced or eliminated.
- Oshyan