You can download videos from youtube/twitch and other sites with yt-dlp like this:
yt-dlp -f "bv[height<500]+ba" video_url
You can use ffmpeg to compress video and strip metadata:
ffmpeg -i input.mkv -s 854x480 -vcodec libx265 -crf 30 -c:a libopus -c:v libvpx -map_metadata -1 output.webm
These are hosted on catbox.moe
Since all videos you watch use same bandwidth as downloading them you may as well download them.
To download right-click -> save link as or to download all webms from this page you can use wget:
curl https://bobega.neocities.org/videos | grep -o 'https://[^"]*webm' | xargs wget