In basically every single performance thread in this subforum someone shows up and recommends this wrapper to improve the CPU performance of Guild Wars 2.
Personally I have always stated that a wrapper can't improve performance by definition as it puts another abstraction layer on top of the existing layers. A wrapper is usually only used to improve compatibility, e.g. when you want to run a DX9 game on Linux, you need a DX9 to Vulkan/OpenGL wrapper as Linux does not support DX9. This costs performance. But some performance cost may still be better than not being able to run the game at all at the targeted OS.
I've bought a new 8 Cores / 16 Threads CPU a few days ago and wanted to give DX912PXY a try since GW2 does not even utilize 40% of my new CPU. My expectations have been low regarding the fact that this is only a wrapper.
Long story short: The wrapper is a double edged sword and I would never recommend using it in general.
The last two points are what I expected. If you want to maximize your framerate in Lion's Arch, then you can use this wrapper. But keep in mind that you will lose a significant amount of performance every time you have a GPU limit.