Thank you. As to the draw calls, NanoVG draws everything directly each frame so this is constant whether or not you are updating. As to the overhead, not too long ago everything was updated each frame regardless of whether it was modified or not, and performance was fine. Worse than it is now, but okay. So I guess it could handle it.

But then again, that's only the default renderer. You can always roll your own and plug it in, kiUi has been designed to permit that.