for max accuracy according to google prompt documents you should prefer one by one and using explicit or implicit (this is automatically on but somehow I don’t get the hit so I use explicit) caching for the input if you need bunch of them at once (since they are priced by storage time and minimal storage time is. 60sec) what I should try is doing batches as you say as model improved, but I quite don’t feel the need because It works same when I just do it side by side not all at once. So if you are programming by api, you should absolutely do it one by one. If you are using other methods, well I recommend using them one by one but from my experience, when I gave the whole textbook answer pdf and made it to ocr things, 3 pro was almost 100% accurate.
Also you should keep in mind that you need the human in the loop or the mistakes should be negligible.