You do NOT want to run NPP and Tren at the same time. I wouldn't anyway. Prolactin/progesterone would be an issue. Sure you could combat with Prami/caber but why do that??
A better idea would be to do a 16 weeker where you use the NPP 1-8 and the Tren Ace 8-16. I recommend test prop for the whole ride BECAUSE you will be pinning more often any way and why not take advantage of the better Prop (or even better ... TPA ... your welcome AY).
If you just want to use one or the other (tren or npp) ... I would have to say tren. but I just love tren. I also like low test high tren ... again ... that is a preference ... tren has a much better binding affinity than test so you have a lot of free floating test that has no where to go.
I have also done high tren high test and got great results but I am not sure it was worth it to me personally.
All of my points/suggestions have come from my own research and trials on myself to see how I responded and grew and the sides I experienced. everyone is not made the same and you have to come to your OWN conclusions on how/what you do based on what works for you
QZ