Feel free to use any methods you wish to achieve the desired results.
From a bit more technical point of view, it always makes more sense to:
- use the controls available inside the material rather than additional tools
- use native Corona tools rather than 3ds Max ones
So it's better to use the controls available inside the Corona Physical Mtl rather than plugging a Falloff map to achieve a similar result (for example, you can enable the Clearcoat layer and adjust its Fresnel IOR). This will give you the most physically accurate results and in many cases will also render faster.