It appears that both of these are supposed to chain post processing effects during rendering. But I don't understand how they differ or why you would use one over another.
The Threejs docs has a sparse post processing page but it never mentions anything about nodes despite several post processing examples using them.
Ultimately what I am interested in doing is similar to this example except I'd also like to add sharpening as well. But I can find zero documentation about the "Nodes" that are being used.