Av1's encoding speed is still a problem right now, but the developers of rav1e encoder state that it is the fastest av1 encoder, and many movie distribution companies contribute to that.
It is worthy to notice that the default qp setting, which is 100, is pretty good for distribution purpose. I added speed 5, tile columns 2, and tile rows 2 based on some benchmark tests.
Here is my setting, and it is pretty simple:
ffmpeg -i input-video.mp4 -c:v librav1e -speed 5 -tile-columns 2 -tile-rows 2 -c:a libopus -b:a 500K -threads 16 output-video.webm