VP9

• GitHub downloads
• webm wiki: VP9 Encoding Guide
• FFmpeg and VP9 Encoding Guide
• ffmpeg libvpx documentation
• VP9 Bitrate Modes in Detail - Google's
• VP9 Tips - Encoding Modes and Recommended Command Line Options - upstream's wiki
• Google Wiki - VP9
• CRF Guide (Constant Rate Factor in x264, x265 and libvpx)
• HandBrake github repo of documentation

By default, vpxenc will use 2-pass method for encoding.

As far as I can tell, there's no default when using CQ mode. I don't know what variables it's using for default when doing a 1-pass encode.

By default, HandBrake uses a CQ of 22.