While Mirillis may keep the hit to your cpu low, it also comes at a cost. It records crap quality. I compared Mirillis and DXtory with the same game and the same render settings and DXtory wins hands down. I'm sure mirillis can be great but at the moment it records dark for me even at 1080p - 0-255 normal or high 30fps with the video exported 1080p mp4.
As far as I know there is just no way to fix this, the quality is really sacrificed for performance and it shows if you really look at whats being outputted. I would love to know how they claim to be able to cap in 1080p without the pc taking a hit at all, it just doesnt seem logical. I bought Mirillis on sale so I didnt really take a hit financially but still this feels like a waste of money, I bought a product that claims to be able to do something it just cannot.. Here are the comparison videos:
Mirillis - https://www.youtube.com/watch?v=1mAM3sIF1H8
capped at 1080p, 30fps, 0-255, High, MP4 AMD APP.
DXtory - https://www.youtube.com/watch?v=sRRoHxOkInU
capped at 1080p, 30fps, standard settings.
you be the judge tell me which you like better