Most portable will be UsdPreviewSurface , but as you’ve discovered, that can vary by app as well.
For example different DCCs may have different opinions on what a PBR is. Blender for example will import it but doesn’t really have a concept of occlusion maps etc…
But yeah in general, maximum portability will be UsdPreviewSurface. Maya and Blender will both generate good reference files in that regard if you’re looking for something to go off of