I have multiple physics materials working on my landscape. As far as I can tell it’s irrelevant to what kind of material you are using for the visual part. As long as you add multiple paint layers to the landscape itself you can assign physics material to each of them.
From WM you need to export one or two mask, then add two or more paint layers on landscape and load masks into them. When you add layer, editor will ask you to same LayerInfo (or something like that) asset. That’s the asset which you can open and set physics material in it.
If you need an example, check my MMT Content project (GitHub - BoredEngineer/MMT_Content: Machinery Modelling Toolkit is a plugin for UE4), landscape on Land Vehicles map should have multiple physics materials assigned.