NVENC HEVC best encoding and decoding settings for 8k

I am trying to encode the DirectX 11 surface using NVENC and it is working very well with h264 up to 4k resolution.

I want to extend the support for 8k resolution with HEVC(h265) but I am not getting the good quality with h265.

Could you please provide me with the best h265 encoding settings which give better quality and better performance?

Also most of the NVENC SDK samples only use h264 encoders.