as the title states, i'm seeing both the default nameplates and the addon's nameplates

I've tried deleting the wtf folder and reinstalling addons one by one. Tried disabling nameplates in the blizz UI but it removed both. I'm not using elvUI or tidyplates.

Those aren't the default nameplates; you have another nameplate add-on enabled. Compilations like Elv or Spartan might have their own nameplate module which you need to disable in their settings.