@Lumeinshin
Is 6mb really that big? Also, sure you saved space, but unless you really know what you're doing, you're destroying the quality too. How much tweaking do you do with the settings? How slow do you allow the encode to be to get small files? Do you test for compatibility? I could easily push 16 reference frames on all encodes, but wind up with clips that Android refuses to play.
@Lumeinshin
Clear enough. I'd say 240p is much to low of resolution, even for what it is. 360p-480p should be a minimum. Very slow is basically the only profile that is even worth using on x264 these days. And placebo, as the name suggests, is just burning CPU cycles for nothing. For animated clips I highly encourage you manually bump up the reference frames (from what I remember 9 should provide good compatibility even for 720p video). And crf 25 is... acceptable. I wouldn't watch a DVD reencoded at that quality, but for what you're using it for it's ok as long as the resolution is decent too.
Very smart use of mono audio though. You could lower the bitrate to 48kbps per channel for most things (so 48kbps if mono, 96kbps if stereo).
@Lumeinshin
In theory you can encode the video and audio separately, maybe with ffmpeg, and multiplex them with mkvmerge. This way you can tweak audio or video independently without redoing all the encode, but meme videos should be short enough that it doesn't matter).
I used to enjoy playing around with these things. Might start playing around again. Maybe make a script for myself. I post plenty of YouTube clips, and want them to be decent quality, but I usually don't go over a certain size, so I end up downloading a lower res version. But I suspect I could get better results if I download a 1080p and do the resizing myself.