I am not very familiar with PBR as a concept. 3D Gamestudio includes diffuse textures and allows you to modify them with normal and specular maps. It also provides a number of built in shaders for various effects. If you are using models to create your levels, as I do, you can use all these things in your game's levels. Also, there is an option to create mipmaps when setting the texture format in MED. I don't know if this answers your question or not, but maybe it will help.