Nametag Information
This website lets you test out custom nametags to see what works and what doesn't. It lets you also see how it will look like ingame! *This website does NOT show the actual font used ingame, so spacing and such might look different. Still if the characters work here it __should__ work ingame.
CS2 nametags use Unicode characters in the UI to set it, but use UTF-16 in the backend to store it. This means that some characters, such as emojis, will still work, but take up more than one actual character in the 20 character limit.