You should know that I've done lots of scanning, but I haven't done this with a phone. So, for what it's worth:
Why do you want to use TIFF? It uses a great deal more storage than the usual jpg or heic. Sure, if you're taking pictures of peacocks and you want to retain the fine detail of the feathers, TIFF might be good, but you're scanning prints, right? Once a photo is pasted to a piece of paper, you're stuck with the texture and decomposition of the paper as well as the quality of the printing. Prints just don't have that much detail to begin with. Is there some special reason you're thinking of using TIFF?
Notes does really well at scanning documents, straightening them up and adjusting contrast and such. To do that, it makes certain clever assumptions about the nature of documents. But photographs are rather different. If you're careful to keep the camera parallel to the picture, and you keep it far enough away that all parts of the picture are about the same distance from the lens, and you use even lighting, then it seems to me that the camera app is better, and the pictures go straight to Photos. I think you should try it both ways to see what's better.
It's interesting to restore prints, and there may well be 3rd party specialty apps that help with that, especially if you're dealing with removing dust and decay and restoring color. The Photos app can help with that, but I've used different programs for different needs. You don't want to lose the original image, though. The Photos app never touches the original, so you can always go back. That's essential. It may depend on what you're working on.
That's about what I've got--others may have more experience with using the phone for this.
