[LBA]Spy.x.Family.03.x264.AAC.720p.HARDSUB.mp4

We have to appreciate the efforts you're doing, it's a fact, however I'm convinced there are much better ways to achieve what you're trying to do.
This is gonna be a bit long so stay with me.

You may notice I'm a huge AV1 enjoyer, especially for low sized stuff. However for weekly releases, I chose to encode 1080p content. Usually that means my releases are around 200-300MB in size (taking into account I have almost twice the audio bitrate).
You're trying to go lower than that, at 720p even, which makes sense, since even today, most anime are still being done by studios with a native resolution ranging from 720p to 864p usually.
It also helps decoding speed by a lot. And it seems it's actually the reason number one why you're doing those releases using x264.
But with some tweaking, you can actually get similar decoding speeds from AV1.
I won't be talking about HEVC since it's pretty well known its software decoding speeds are pretty bad, which can be explained by the democratisation of hardware decoders soon after its release.

Using a mobile 4 cores pentium machine running at around 1.9GHz during those tests, never consuming more than 16W, I managed (using the latest version of ffmpeg to have the latest decoders) to get around 800 fps playing your encode. It took 50s to finish the decode benchmark test.
Using tweaked SVT-AV1 settings, I managed to go even lower at 46s, with an average decoding speed of around 900 fps, while having a lower filesize and a similar quality overall, except during an instant in a dark/fast-paced scene from the flashback from episode 2 where it blurs quite a lot, but in action it's not that noticeable, and considering you even say it's meant for people that don't care about that...

However that was really an extreme test to actually see if AV1 can even reach AVC's performance in decoding. Using more sane settings, with the goal in mind to achieve what you're doing here, I get a decoding speed of around 700 fps with the benchmark lasting 54s, a filesize of 81MiB just for the video stream when yours is 106MiB, a better quality in every well lit scenes, still and moving, and overall comparable quality in still dark scenes, with some blurry results in extreme dark/fast moving scenes.
And it wasn't even slow to encode since it was done using one of the fastest preset of SVT-AV1 and it only took 7 min to encode on my 6 cores 8700K. Yes, 7 minutes.

All of that to say that in reality, any device that can play your encodes can also play tweaked 720p AV1 encodes without issues.

But even then, I don't see the point of going to such extremes. If a portable 4 cores Pentium machine can do 800 fps in AVC or tweaked AV1 playback, you'll need to go really far to find something that cannot play any of those at realtime speeds...
Thus, using slower presets, I can get even better looking results at 72MiB with a 11 min long encoding, and a decoding speed of 500 fps.

And trying to play this last encode on a Snapdragon 430, 3GB of RAM device using the latest MPV, I didn't drop a single frame.
I guess it's enough to tell you it's about time to abandon x264 for low sized releases.

Thanks, I appreciate the feedback. My main focus is small filesize, with quality being "good enough" as the 2nd priority. It's mostly to serve people stuck with internet caps and such. Small filesize allows them to try more shows and decide which ones to spend their precious bandwidth on. For me, [QCE] and [LBA] are just "give back to the community" as thanks to the scene that allowed me to get into anime when I was younger with very limited internet myself. Decoding and encoding speed are 3rd priority. The settings I use allow me to typically encode in about 5mins on my r5 3600

I doubt I'll be doing this for long; I'm just hoping my work will inspire some others to get into encoding to expand the scene more. It's also why I hardsub and don't mask my settings. So far it's worked - several people have asked about the process and looked into how to do it, either because they have anime that they'd like to reduce the filesize for, or because they hate hardsubs and want to re-do it with softsubs. No doubt these people will go on to look at x265 and AV1 once they realize the limits of x264. When that happens, I hope you'll be there to guide them

Everything you mentioned is interesting, and I agree. Based on the info you provided, if you did AV1 720p encodes I'd probably stop doing what I'm doing. Unfortunately for me, my knowledge is stuck in 2010 with x264 when I was still into video stuff at the time. I haven't looked into x265 or AV1 much so I don't know anything about them, nor do I have much interest in it these days. The only other encoding that I do besides anime is stuff for my parents, who are still using the TV I bought for them back in 2011 (which can't handle x265 or AV1). I know I could probably make better quality, smaller encodes using AV1... but I'd have to learn it first. That simply isn't something I have a lot of time for these days (and I won't be part of the scene much longer anyways)

Cheers though, and thanks for the professionalism

You are right, device compatibility including old TVs is also important. I understand what you want to achieve doing those, it's really respectable.
I can't release 1080p AND 720p weekly encodes at the same time right now (but it's planned for the near future), so for now I guess it's fine that way.
But I'm definitely interested in helping people adopt AV1 in the situations where it's better suited than other codecs.

Also, just to clarify, AV1 encoding settings unfortunately don't get put on an encode's metadata, so unless I share my long and tedious command line for each encode in the release description, no one can know what has been used to encode them. It's not by choice that they are hidden.

Thank you for your clear answer :)