Use a system font stack. Both macOS and Windows come with good font choices, and Linux … is Linux, more often than not, users are not even aware of typography or why it matters.
Of course. It’s just my subjective experience that most don’t. It’s to the point most don’t know what ligatures and stylistic sets are. Most Linux software lacks basic OpenType features support.
Since a noticeable at least portion of Mac OS users have some artistic vein one would argue for Mac OS users. For Windows my personal opinion is the average user has no idea. I think for Linux/BSD etc there is a part of users that know or have some idea but don't care enough personally. I comment from experience -- not aware of any study that looks for correlation :D