There are a handful of groups putting out what I would consider decent AV1 encodes. A couple PTs allow them, and there are groups on 1337x. Just grab a couple from each tag you can find and see if they meet your needs. Generally speaking, look for groups which note their source, which encoder they are using, and ideally what settings they used in general.
AV1 has come a long way fast, but in my experience a good x265 encode is still better for live action.
A properly muxed mkv will display the resulting audio bitrate. And if you use opusenc, it will embed the encoder settings in the track.