I still have an old notebook with an AMD/ATI card and it suffers clipping, lags etc. no workaround from any version of drivers in years !
Install a distribution that includes recent drivers: mesa+kernel (e.g. Antergos). That should be all you need. Even the tiny GPUs in AMDs APUs work great for me using either the OSS or proprietary driver.
I am just going to be the ugly kid in the corner with the humpback and the protruding eyes who has not learned to run with the pack, and never will.
The benchmark is a great opportunity! One to learn from how to write better code and to measure existing code so it can be improved further. And it is of use to everyone - for Nvidia, for AMD, for Intel, for the Open Source community, any developer really. And what leads to better code leads to happier end users.
I will now go back to my corner and let the experts name and shame the heck out of the benchmark and the results. I do know why you are really doing it (so you can make sense of it ).