It depends on the meth setup. AA's kit is more like a charge cooler to keep the IATs down. I don't think AA changes their tune for the meth.
Something like HPF's meth kit on the E46 is a power adder and the tune accounts for it. That is also a somewhat complex system that has a lot of safety nets. From what I know, it is a reliable system as well. My want to look there, look at their dyno charts between the meth and non-meth systems. Might give you an idea on how much power you can get.
IMO, I don't think you'll get good/safe results unless you have a REALLY knowledgable and good BMW tuner nearby and have lots of money to throw at it.
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red