It didn't really help for a 1920p h265 though (I'd have to hunt to find a h264 at that resolution, those files tend to be huge). It might have been better, very hard to tell, but the video was still way behind the audio.
According to this[1] table, your card won't decode H265. For H264 streams, add `--vo=gpu --hwdec=auto' or `... --hwdec=nvdec'. (The first is what applies to all HW.) Then, use `I' (capital) to see if mpv is using HW decoding. Toggle with `Ctrl-h'. -RVP [1]: https://en.wikipedia.org/wiki/NVDEC