[Hectic]

If the pdi hop up is the version 2 it should work with all heads. The original only worked with the pdi head.
I'm not sure what you mean by AA. Must be some clone brand?
You can prety much flat/rhop any hop up however the pdi with the dual adjustment arms may not be the best platform.
I personally prefer the stock or laylax hop unit with some minor modifications to the hop arm to allow more hop application.
The vsr hop up is damn good. I run a 500fps vsr 10. I run the laylax hop up. I reach out 400+feet with .36-.43g ammo and never need more than half hop applied. Unless your trying to lift some .66 or beter you shouldn't really need a flat/rhop