[rulezyx]

This (level, name) is not a texture and you can't customize further without using scripts or addons.

The level on/next to the nameplate is not a default setting and I dont know what addons you are using but it simply doesn't exist with the default retail nameplates.

If you play classic WoW you have to use a script(macro) or code(addon) to hide it.

I don't play classic anymore and I would still suggest you to take the addon or another nameplate addon that gives you the options to change those things.