Your question is confusing but I think it's two questions:
1. Is there a difference between carry-on-old-X-ray and carry-on-new-X-ray in the danger to paper?
2. Can the carry-on-X-ray tell that a box of paper is a box of paper and that it does not need to be opened?
Clearly, I'm not an airport-security or photographic-film-and-paper expert and so I can't answer with absolutely certainty. It's my belief that, for film/paper, the difference between old X-ray, new CT X-ray scanners, and checked baggage X-ray is mostly a difference of intensity. I think they use different luminosities, but not significantly different energies of X-rays. CT scanning allows them to get a computed 3D view of your bags contents rather than a 2D picture, see
https://www.tsa.gov/computed-tomography
Next, does the X-ray give information about what the items in your bag are? This is clearly "yes it does" but to what degree of specificity? If you've looked at a X-ray scanner display, they are usually looking at a false-color picture with 3 (or more) colors, even on the older X-ray machines. The machine uses the different amounts of absorption of X-rays at different energies to measure some combination of the density and the atomic number of the materials. (Heavier elements absorb more and the amount depends on X-ray energy.) There are plenty of webpages that show how this works, although they're often from security companies trying to sell upgraded X-ray machines. For example:
https://www.wg-plc.com/article/6-colour-imaging-x-ray and
https://www.teledyneicm.com/security/how-to-decode-an-x-ray-image/
So they can tell the difference between organic matter and metal, and so on. It's my belief that they made you take laptops out of the bag (before CT scanners) because of the battery, which is a rather dense block of stuff surrounded by wiring, and they wanted to get as clear a view as possible.
The box of paper is going to look like a block of, well, paper. Like a large book. There are organic materials that they might be interested in that could look similar. The water content of food sometimes causes them to want to inspect it - I've had a screener open my bag and look inside to find my lunch (they haven't
confiscated my lunch, yet). For obvious reasons, they don't tell members of the public how exactly they differentiate between threatening objects and your lunch, or your box of paper. So I can't guarantee that they will let the paper through, but they should have a good enough image of the insides to tell the difference between a stack of paper vs a wrapped bag of drugs or a bundle of plastic explosive with wires sticking out.