So far you haven´t mentioned what you want to accomplish. Only problem seems to be the audio. You have to check the hardware configuration for this. Running NCS X server with dxva2 should not be a problem. DDA is?
Apart from the driver what can the graphics card decode? What do the camera send, h264 or h265?
Why change graphics card? The decode GPU load is only around 55%. The CPU load is 96% which is high, but it works. I am running systems with cpu load of that also and it is ok. Change to a more powerful graphics card will not lower the cpu load. If you want to decrease cpu load while keeping camera resolution and fps you need a more powerful cpu / add more cores.