I have no intention of misleading you, and appologize if I have done. As I stated in my original post I had gone through all three UI settings and was experiencing tearing in all of them. I don't know what has changed in my setup since then but UI1 does now seem to solve it, UI2 masked remains to be re-tested.
I wasn't aware that playback in Kaffeine was affected by UI settings, which is why I had left the UI2+alpha setting during the later testing dispite reading about common problems with it. It's now evident that this was a poor assumption, and I appologize for not stating it as one. Sorry for wasting your time.