Overview
Basic resizing preserves the original image exactly but does not add detail. Model-based upscaling adds sharpness but still may not produce the best possible facial, hair, or texture detail.
Manual muting is simple but depends on a fixed seed. Forgetting that setting changes the image between the inspection and upscaling passes.
The Image Chooser requires an additional custom node and restart, but it avoids regenerating an image and offers a cleaner selection process for batches.
A 4x model creates a very large output. The chosen scale should match the actual delivery requirement rather than being increased automatically.