PBR is a rendering technique that many modern game engines utilize. CSAE has introduced this technique to improve the rendering quality of AWM.
Note that CSAE hasn't introduced other graphics techniques yet, thus you should only expect some special effects instead of the whole video quality from PBR.
Before you get started, make sure that your GPU is capable of PBR. See the release notes of Build 1500.
PBR is only available for .mdl model files, and uses a fixed rendering algorithm. There're only several parameters you can tweak.
PBR does not include other visual-enhancing techniques like dynamic reflections, ambient occlusion, or parallax mapping, but you can use normal maps (only available in PBR) to present more details.
Model parts that have textures using PBR will upload their information to the GPU at load time, whereas ordinary rendering in this game engine uploads the model information every time a draw call occurs, which is much less efficient especially when it comes to high-poly model rendering.
CSAE uses Image Based Lighting (IBL) to fake reflections on the model. This may be the only rational solution. You may NOT expect Ray-Traced Reflections or Screen Space Reflections to be implemented in CSAE, as they need significant changes to the rendering part of the engine.