Both of these shaders are built to be applied on a single flat surface such as a plane or quad. For heirarchy setup you can see that the prefabs using these shaders have an empty root game object, the plane at the base of the object and the content positioned above that both as children of the root object.
Camera grain is a unique feature to ARKit which produces a tileable metal texture to match the visual characteristics of the current video stream. In Unity this is surfaced as a 3D grain texture through the [ARCameraFrameEventArgs](https://docs.unity3d.com/Packages/com.unity.xr.arfoundation@4.1/api/UnityEngine.XR.ARFoundation.ARCameraFrameEventArgs.html). For the shader sample this grain texture is then applied to a custom shader graph that also creates visual noise on the object. This effect in general is very subtle and more visible in darker areas where the grain on the camera feed is also more apparent.
> Compatibility for 2020.2+ version of Unity is due to how 3D textures are handled and managed
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