I care mainly about archiving, so 1FPS encodes for 24fps content is within the range that I consider okay.
However, I ran into issues with decoder speed too; whatever codec Kodi was using 18 months ago struggled to decode high-bitrate 1080p AV1 video last time I tried. Maybe this weekend I'll try again on the current version of Kodi.
Try encoding with a "low-latency" or a "fast-decode" parameter, and see if that is acceptable to you. Keep in mind not all AV1 encoders are created equal.
If you're on Windows I recommend using StaxRip for encoding.
I'm on Linux, currently using ffmpeg for encoding. I'll look for options that might improve decodability, but I seem to recall I had to go pretty aggressive on both of the two av1 encoders I tried to get any savings vs H.265
It depends on what bitrate you are targeting, and the source content.
AV1 does not outperform H265 at high bitrates (and in certain cases, medium bitrates). What is considered "high bitrate" is dependent on source content, but a good rule of thumb is 40 MBit (think BluRay quality) or more for 4k content almost always goes to H265.
For AV1, depending on what you are encoding, and how much extra time you want to dedicate to experimentation, take a look at grain synthesis (you will want to test decode capabilities on that one).
However, I ran into issues with decoder speed too; whatever codec Kodi was using 18 months ago struggled to decode high-bitrate 1080p AV1 video last time I tried. Maybe this weekend I'll try again on the current version of Kodi.