Just to clarify, based on the question 2 things:
1. That GPU will work fine with that APU with only its own Nvidia drivers installed.
2. You cannot install the drivers for the APU's graphics as well, they do not work together, it will not boost performance. I doubt it will cause a major issue but could cause a conflict, however most likely it just won't do anything since you will not have a monitor connected to the APU.
There is a scenario called Dual Graphics where the APU can work with an AMD GPU, but they are low end models and it works pretty poorly, and as I said, doesn't do anything with a Nvidia GPU.
Innocent Demon :
The APU is uninstalled. The only thing that is installed is the GPU driver.
So i was thinking if i can boost my performance...