For YouTube videos you can use PiTiVi (free open-source based), usually I use for my official videos indeed.
Refer/Download Pitivi: http://www.pitivi.org
PiTiVi looks like Windows Movie Maker clone to a certain extent. You can also optionally install your own extra codecs (audio, video) and so on.
However I doubt it can offer superior professional video quality editing/processing.