So I'd like to make sure I understand this properly. I know I understand sub-pixel arrangements of RGB vs BGR. The following image makes a whole lot of sense to me where the text anti-aliasing is crap because it's configured for RGB but the subpixel arrangement is actually BGR. In this image, you can see that the anti-aliasing is actually backwards on a per-pixel basis. In other words, as the A slants up, you can see "jaggies" sticking out, and likewise when it's slanting down. If these pixels were RGB and not BGR, then those "jaggies" would be flipped which would mean that they'd be along the letter providing for the smoothing effect that anti-aliasing is meant to provide. So this all makes sense to me.
And a neat side-effect of this understanding is that if you take a BGR monitor and mount it upside down and flip the orientation by 180 degrees in Windows (or presumably also on a Mac), you have effectively turned your monitor into one with an RGB subpixel arrangement. Neat!
But here's my question: What happens when I rotate my monitor by +/- 90 degrees? How does Windows and MacOS handle this? Are they smart enough to know that instead of having subpixels that are side-by-side that instead they're now stacked on top of one another? Or does this just result in botched anti-aliasing that is going to strain my eyes whether I realize it or not? There's some info on this site but it appears to be dated and I simply don't know if anybody has a solid answer to this on Windows 10 (what I'm specifically interested in since that's what I use).
Would love if somebody much smarter than I am could chime in on this! :-)