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WelshPaul - a final thought, perhaps, although you're maybe not in the mood.
There's a fundamental difference between Linux and Windows, in that what you see - the Window manager, the graphics effects, the interface - is not a core part of Linux in the same way as it is on Windows. So, all this talk about window managers is about changing the way your particular installation of Linux appears: XFCE, Gnome, KDE, Flubox, LDE, they all do broadly the same thing but with different levels of "eye candy". Windows gives you a choice of just one, as does OSX on Apple.
Compositing is a term that comes up a lot in the film industry, in that it's the process of manipulating and combining digital images: think green screens and impossible effects. In terms of a PC, then, compositing is the process of manipulating the desktop and window images so they look really swish - 3D effects, swoosh in and out, transparency, shadows, and so on. You may want these, as they look cool, but they typically add nothing to the underlying drag/resize/overlay functions, and just take up CPU power. So, as a rule, lightweight window managers do without these bells and whistles so as not to strain limited CPU and memory. (If I remember correctly, Microsoft introduced compositing with Vista, hence the Aero theme and all those glass effects).
On your system, which may easily have the grunt to run all those effects, you clearly don't *need* a lightweight window manager. However, if there is a clash between Compiz (which is the compositor you have) and an outdated graphics driver, then you can see how you've ended up here. Kodi in itself doesn't care what window manager you use, it's more that it's showing up whatever clash/bug is biting you. There's probably some way of disabling or removing Compiz entirely, or trying a different compositor if that's where you want to go; if you just want to use the thing, then try a couple of variations and see what works and what you like.
FWIW, I'm typing this on a 4th gen overclocked i7 system - that runs a non-compositing version of Xfce. I don't care too much for fancy effects, and am happy with a lighter window manager as a result. The beauty of Linux is that you can, of course, install pretty much every different desktop at the same time if you wish, and just see what works: the "Kodi skin" analogy was that each window manager is just that, a skin for the underlying operating system. Think Windows themes, but really taken up a notch.
