I need advice about Guitar Hero software & controller compatibility for Wii?

If you are a Guitar Hero expert, can you please explain this is layman’s terms:

I want to buy a Guitar Hero controller (the plastic guitar) for someone who has Guitar Hero 4: World Tour for Wii. They already have one guitar & I’m getting a second one. So, what I want to know is: should I be looking for a certain guitar that is compatible with Guitar Hero 4 or will any Guitar Hero controller suffice? (are there certain guitars depending on the version of the game you have)?