Courier New is a bad font that no one should choose to use. In typical font-weight terms, where Regular should be 400, it’s 200–250, because it was improperly digitised, not taking ink bleed into account. Windows put some hacks into ClearType to make it render a little less badly, but they’re not dependable these days.

(“Courier”, as provided by macOS, is fine. But Courier New is irredeemably bad.)

Concerning font-family declarations, if you’re doing something like `"Courier New", Courier, monospace`—please just write `monospace`.

(I’m not going to address the font size.)