You can delete the WTF folder, it will be recreated.
I'm not sure about the WHOLE Interface folder though. I mean it contains some blizzard addon folders that you might need to keep. Then again maybe not.

In any case, to remove an addon you should simply remove that addon folder from the "Interface/Addons" folder. You can also remove the WTF folder to remove the SavedVariables as well, but not usually necessary (and a lot of work to reconfigure all)