First off, I’d access and bookmark Apple’s iPhone User Guide for whatever model you have. Study it, especially the Camera section.
In your Settings App, go to Camera, go over all your options, and make choices that best meet your needs. Most image quality options/settings are in “Formats.” The highest resolution original will give you the best output options.
I’d start with the provided Photos App first. If you find it wanting, determine your needs and shop carefully.
I don’t understand your “scale” requirement, but if you’re talking about prints, I’d look for a printer you can have a face-to-face relationship with.
Good luck! …