And as expected, AI only answers part of the problem.
While it is true that sub-pixel alignment is horizontal when in landscape mode, and the default configuration for sub-pixel alignment optimizes for this…
- macOS does not do sub-pixel anti-aliasing.
- Windows ClearType includes a “Clear Type Tuner” application, which you should run on each of your displays to optimize its algorithm. As a part of the tuning process, it will select the correct algorithm for horizontal-vs-vertical subpixel alignment and the order of subpixels (RGB vs. BGR).
A Studio Display is a retina-doubled 1440p display (5120x2880). When configured for 2560x1440, there will be 2:1 display scaling. There is a certain amount of anti-aliasing involved, but macOS should be anti-aliasing your native 1440p display as well, which I would expect to be fuzzier (since it’s anti-aliasing a lower native resolution).
Do you see the same fuzziness in landscape mode? If so, then there may be a bug in Apple’s anti-aliasing algorithm, although I wouldn’t think it would matter without sub-pixel optimization.
I’m surprised True Tone affects the Acer. I thought it is designed to only work with displays that Apple has certified for TT compatibility.
Have you run color calibration on the two displays?
I wrote about this recently. Calibration will help the two displays look much more like each other. You can’t do a perfect job without special hardware, but Apple provides a software tool that will definitely help.