HandBrake is a tool for converting video from nearly any format to a selection of modern, widely supported codecs.
It is a similar story here – the four cores, eight threads of the 1500X deliver solid performance in Handbrake. It is not class-leading, but we wouldn't expect that considering the price of this system.
The X370 mobo would have been a good choice if the PSU could handle crossfire. The CPU is also a bit on the edge for crossfire – a 1600 or 1600X would have cut it imo. Then again, those two things would have driven up the price. I have to agree that a B350 mobo would have been the best choice.