Hello, finally, our rx5700 arrived.
Below is from developer:
In the test, the VideoProc cannot produce mkv 4k 10bit hevc , and they may have some bug or misleading on showing the info, the output setting is different from what you set for DVDFab.
Please compare the output file information, you can check with free tool .
And you will see that VideoProc cannot change profile as shown in my pic, also in your .docx file posted in #3.

The MediaInfo shows that output is not 10bit.

We checked the AMD official SDK, AMF, and it does Not support hevc 10bit encode for now (2020/05/08).
If you find something different from ours, please let us know, thank you.