&wcap update - now it can encode video to 10-bit HEVC (main10 profile). Theoretically it increases quality of image as there is more resolution for color values in conversion to YUV. But it depends on how GPU implements encoder. In practice it will be very hard to see any differences. From my non-scientific tests with Nvidia, it seems it encodes better - on some content it gets ~10% smaller video files than 8-bit HEVC.

Not all GPU's support encoding to 10-bit HEVC. Check your GPU support here:
Nvidia: https://en.wikipedia.org/wiki/Nvidia_NVENC#Versions or https://developer.nvidia.com/video-encode-and-decode-gpu-support-matrix-new
Intel: https://en.wikipedia.org/wiki/Intel_Quick_Sync_Video#Hardware_decoding_and_encoding

Get it on GitHub: https://github.com/mmozeiko/wcap