I tried to download a medium set of youtube videos, proceeded with default settings and recommended steps. I was bit suprised why download is using so much CPU but ignored this at the time.
Just to notice at the end, that it wasn't really clear that all videos will be embedded with big ass QR code and only reason it took 20+ minutes to download single movie was because extension was busy with embedding it with their plea to give them money.

Uninstalled immediately after that, not planning to return.