Great article that really helps me understand the various presets of AV1. I re-encoded a 8gb 1080 h264 with AV1 preset 4 and crf 22. Came out just under 800mb. I do see some compression artifacts in the resulting video, but nothing serious and the bandwidth savings is great.
I have also found that encoding speed doesn't change much between presents as much as just scaling the output to 720 instead of 1080. Which is what I do for files that I'm ok with being standard HD res to get that almost 2x encoding speed.