I've just tested both `intel-svt-hevc` and `intel-svt-av1` from AUR on my 8-core i7-4790. Here are the results:

    Initial file:
    sintel.y4m  1280x544  21G
 
    HEVC:
    FPS: 140.65, File size: 114M

    AV1:
    FPS: 34.891, File size: 39M

Default profiles, since I'm not very familiar with AV1. HEVC is only 4 times faster here, but the AV1's output is 3 times more concise.

So AV1 looks very promising considering it's in its infancy yet.