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It is simplified, but generally speaking these are main possible paths with default settings.
X axis is market share (with some guessing).
I know a small examples of renderings could be included for better understanding, and I will post this & other refinements later.
A few things not mentioned:
Linux with FreeType rendering, but I have no idea how many people use subpixel rendering or other settings. Each setting has probably less than 1% of users.
Quartz rendering does also other types than subpixel AA, but I would say they are in minority (I really don't know).
There is also an old version of Safari, with Quartz rendering on Windows with default setting.