Toolbag is doing a good bit of tricks behind the scenes to get the subtle surface shading and reflections. The part that you will be missing is having a proper environment to reflect and shade the surface. Toolbag lets you change up cubemaps and environment maps to make it seem like its in different lighting conditions. If you preview your object in unreal without having some type of environment either faked (hdr on a sphere with inverted faces) or and actual scene you will never be able to replicate the results in a blue sky with a checkerboard ground. PBR materials and unreal are powerful that they let you do amazing things with specular and diffused reflections, but the real magic is always both the object that is doing the reflections and the stuff that its reflecting ie, car advertisements that have white cards placed above them for tight spec hits on incidence angles.