It's recommended leave hardware decoding disabled.

If you want to enable it read https://mpv.io/manual/stable/#options-hwdec to understand which option is best for you.

Determines when to save and restore the position of previously played files.

• -1: feature is disabled
• 0: save for all files
• 1-9999: save for files longer than the set value, in minutes

When enabled it automatically skips chapters containing certain words/characters.

The words/characters to skip are defined as a comma separated string.
The match is not exact, meaning op will match words containing it like opening

Haruna uses youtube-dl to play online videos. Some sites offer multiple versions of the video/audio (different codecs, resolution). This setting allows you to configure what version of the video/audio youtube-dl selects.

More info: https://github.com/ytdl-org/youtube-dl/blob/master/README.md#format-selection