Radeon Software 18.20 vs. Mesa 18.2 RadeonSI/RADV Linux Driver Performance
When running Dota 2 with OpenGL, RadeonSI on Mesa 18.2 remains substantially faster than the PRO OpenGL driver.
While running Dota 2 with Vulkan is a much tighter race between the competing Vulkan drivers... The RX 580 and R9 Fury delivered neck-and-neck performance between the two Vulkan drivers while the RX Vega 64 was faster with the PRO Vulkan driver. That's not too surprising as we have seen the PRO driver stack offer better Vega support previously as the Mesa-based drivers are still optimizing around Vega/GFX9.
Dawn of War 3 with Vulkan would lead to the game simply crashing with the 18.20 PRO driver.
F1 2017 with the Radeon Software 18.20 Vulkan driver also wasn't panning out.