I've recently heard that the best render quality is to render the video in the same bitrate as you recorded the video in, but the problem is that I have no idea what the bitrate is.
I have every setting maxed out in MP4 AMD APP and bitrate to max and quality to High.
Specs:
* CPU: Intel Core i5-3570
* GPU: R9 280X
* RAM: 12GB 1600MHz
* OS: Windows 10