They're good to combine actually, the extra AKG from the NO2 will increase your creatine uptake (from the V12). You won't be getting too much of anything that you can overdose on, so don't worry about that. V12 is just creatine, glutamine, taurine, arganine, and Betaine-Glycocyamine, but you don't get much of anything but creatine from it, so using extra any of the other ingredients will give you some extra results.
As for V12 and ephedrine, don't do it. AKG is a vaso-volumizer, and ephedrine is a vaso-restrictor. They perform exact opposite functions. If you are trying to lose weight, go with the ephedra, bulking, then go with the AKG.