www.makemkv.com

I typically use Handbrake for all my DVD and Blu-ray conversions, once I have an mkv file.
I am using Mac X Video Converter Pro for my 4K mkv files, since it typically takes about 30-45 minutes to convert
a 4K mkv file into an mp4 that I can use with iTunes and Apple TV 4K. Handbrake will typically take over 45 HOURS and comes out with a very mushy, dim looking file but it is also a fairly small file.

My only issue with Mac X is the size of the file once the conversion is done. A typical 4K mkv file will run about 55 to 65GB in size. Mac X will knock it down about 20-30%. Needless to say, that chews up a lot of hard drive storage space.

Any thoughts or ideas would be appreciated.

Handbrake does not do HDR video right now, which is probably why your colors aren't as "vivid".

It also defaults to "higher quality" than speed in the most recent versions, while it is likely that VCP is defaulting to speed, and MAY be making use of the hardware encoding available on newer Macs... that also explains the size. You can adjust the parameters on any encode to vary the speed by massive amounts.

Software encoding is not as fast as hardware, but the quality is easier to tune. I can get 270-300 frames per second with a QSV encode, or as low as 1 fps with a high-quality software encode, from handbrake. The QSV encode will be larger and lower quality, because that's how hardware encoders work; shortcuts are taken to make it fast.

There is a saying in video encoding - "Speed, quality, size. Pick two."

Hey, if you want to convert video files to other plain video formats like MP4, MKV, etc., then you could take a try of the Media Converter Mac. It can help you convert video files with high quality and allow you to edit the videos.