Hevc_nvenc vs nvenc_hevc

General Support / Questions Hardware Encoding
2

That’s just a naming convention, it doesn’t change the actual encoder. There is only one NVEnc encoder for ffmpeg and it depends upon your NVidia driver for capabilities.

http://ffmpeg.org/pipermail/ffmpeg-cvslog/2016-June/100774.html

See this thread for details on recommended pascal driver versions.