Similar except that you can see the difference between lowercase and uppercase.

Kind of. Imagine if capital letters looked identical to regular letters just with a different byte representation, but Windows preserved them regardless.

Well, it turns out that Unicode can represent a lot of characters by way of different possible encodings (for example é could be a single codepoint, or the codepoint of e followed by the codepoint of an acutely accent).

Notes does something like this for some reason. The quotes that are used in the Notes app that are then copy pasted into other apps like Terminal or a code editor are not the same as the quotes we use every day. I think some apps are smart enough to fix this by default (perhaps IntelliJ?) but otherwise it’s the source of a non-negligible amount of annoyance if you like to use Notes for whatever reason

that’s because curly quotes are different characters from the straight quote characters that you can see on your keyboard. Some apps will convert straight quotes to curly quotes to “help” you.

https://www.cl.cam.ac.uk/~mgk25/ucs/quotes.html

in system settings somewhere you should be able to disable smart quotes (or something like that).

APFS does the exact same thing with capitalisation as well (presuming you're using case-insensitive APFS, which is the default).

I thought the default has been case-sensitive for a while.

You thought wrong.

Windows has a flag for that for it to respect case. But it would probably bug out a bunch of programs. I usually see it with samba shares. But you can get it to do it on the local filesystem too if you try hard enough. Also it is a bit of a pain when it does happen if you get two files with the 'same name'. One file will be basically invisible to most of the normal windows tools.