Relationship between Virtual Shadow Map and Contact Shadow

How do I make a specific actor ONLY use Contact Shadow while other actors use Virtual Shadow Map?

I’m asking this because this video says that, in Fortnite, grass only casts screen space contact shadow as an optimization for Virtual Shadow Map.

The document of Virtual Shadow Map also mentions using contact shadow for foliage:

How do I prevent grass from using Virtual Shadow Map? I thought Virtual Shadow Map was a project-wise setting.

I’m really confused with these terms. So normally Virtual Shadow Map and Contact Shadow work together? Shadow Map is like the real big shadow, and Contact Shadow is like the shadow at the contact area, sort of a heavier version of ambient occlusion?

Thanks.