The reason the 9.7 has nx/gx mix is to hit a price point while using a carbon main triangle. The 8 is aluminum and less expensive to make the frame so roughly the same price point by putting more GX on it.
NX is heavy but it shifts ok. It's pretty durable. The biggest weight difference is in the cassette which is close to 1/2lb heavier than GX cassette. The biggest problem is they have to change the driver on the rear hub if you want to upgrade to GX- which isn't hard, it's just another expense. All the NX components will work interchangeably with GX (or any other eagle drivetrain) except for the driver issue.
It's a good bike as it sits and the frame is upgrade worthy if you feel the urge.
***ah, Mitch beat me to some of that. cheers.