Hello again. When I have tried https://www.amara.org I simply logged in, pasted the URL of the Youtube video I wanted to subtitle, added the subtitles in my different language and then once saved, they could be downloaded in different formats including .sbv .
So I had imagined this would be how you would translate the HQ videos, and I would then upload the subtitle files the appropriate video.
I haven't explored the crowd-subtitling which you linked to. I haven't seen aegishub either, and it does look interesting.