About
It holds a FBodyInstance BodyInstance initialized in UPrimitiveComponent::OnCreatePhysicsState.
Most (all?) of their physic settings are in BodyInstance and FBodyInstanceCore.
Some special settings like the constraints are in BodyInstanceCustomization.cpp (FBodyInstanceCustomizationHelper).
For Constraint details check Body Instance and Constraints
Classes
flowchart TD
UMeshComponent --> UPrimitiveComponent
UProceduralMeshComponent --> UMeshComponent
UMeshComponent --> UPrimitiveComponent
USkinnedMeshComponent --> UMeshComponent
UWidgetComponent --> UMeshComponent
UBaseDynamicMeshComponent --> UMeshComponent
UDynamicMeshComponent --> UBaseDynamicMeshComponent
UGeometryCollectionComponent --> UMeshComponent
UStaticMeshComponent --> UMeshComponent
USplineMeshComponent --> UStaticMeshComponent
USkeletalMeshComponent --> USkinnedMeshComponent
UPoseableMeshComponent --> USkinnedMeshComponent
UInstancedSkinnedMeshComponent --> USkinnedMeshComponent
UInstancedStaticMeshComponent --> UStaticMeshComponent