NVENCC is the enhanced version of the normal NVENC we alredy know, It has better quality than the normal NVENC and can encode at higher bitrates without losing quality. It also supports more video formats and resolutions than the normal NVENC.
More info about it:
rigaya/NVEnc: NVENCによる高速エンコードの性能実験 (github.com)
I used this encoder in other software, and the truth is that the encoding quality of the output video is much better than the normal NVENC.