Re: Differences between the preview and the final render.
To be 100% sure the preview is equal to the the final version it would have to run just as long. The final version in that sense is just another version. To minimize the change on differences you should check the preview at 12%, 25% ,50% and at 100%. The last three % require horizontal and vertical scrolling and a lot of GPU (memory)
I have asked for high quality preview before, but Kolor refused that saying to then better do the rendering.