It's under "Adjust ClearType text" on the control panel in Windows 7. It's also known as "ClearType Text Tuner."
It doesn't specifically ask you to pick your subpixel layout, but rather shows you a bunch of different renderings and asks you to pick the one you think looks best.
You realize we are talking about a 2560x1440 monitor right?
Depending on your DPI settings, one can consider turning off subpixel smoothing at this res. At 4k you should certainly consider it. Plus, I'm sure various implementations are better than others. Does the iPad have this problem?
True, it's a 2560x1440 display, but it's not “retina“ yet. There is still a big difference with and without subpixel rendering, especially for smaller texts. Well, at least to my “retina” spoiled eyes. YMMV.
iOS does not use subpixel rendering at all, possibly due to the inconsistence of text rendering in different orientations.
That requires having a stand that can accommodate the monitor that orientation - something neither of my existing displays can do. And you've just moved the problem around since a wider display would still be preferable.
I'd be really happy with three huge 4:3 displays but that will never happen.
The output quality depends on the panel type. If it is IPS like these, then viewing angle doesn't matter but some other panels look awful even from a slight side angle.