Hi mate, welcome
If you only want low 200rwks, i would say a power fc will get you there fine. Of course the mods you have are fine, but you may need a fuel pump. If you decide to go with a power fc, u'll notice so much more mid range punch just on the standard turbo.
If however, you wanted to go for the GCG highflow, although you dont 'need' an aftermarket ecu, to get the most out of the turbo, you would definitiely need one. The standard ECU wont be able to keep up with the changes in air flow being pushed through the high flow. However, if you keep boost low, then it should be OK.
Ideally, if you could get both, then youd get the most out of the highflow, along with some bigger injectors and afm.
however, if you were to choose one, my adivce would be to just get the power fc. Youd be making the most out of the stock turbo, itd be better on fuel and better for your engine, generally
cheers,
Anton