It is true that .jpg recompresses the file each time you do a new save, but good programs allow you to choose the amount of compression used, and if you don't allow too much compression you can keep sufficient of the original picture information through "more saves than you'll live to make."
As a practical matter, many scanners allow you to scan at real 1200 dpi or more, but unless you're planning to enlarge to billboard size it's not very practical to do so. Scanning at twice the resolution you're likely to use, and using a low compression, and NEVER RECOMPRESSING the original, you can be confident of keeping what you pick to start with. Opening, and closing a jpg (without saving) doesn't affect what's been stored. Copying and Pasting a file doesn't affect the file. Opening and saving again does.
You can, in fact, save a jpg "uncompressed" so there's no loss, although few image programs let you do it that way; but a true uncompressed jpg adds a "JPG file header" so it's larger than a RAW or BMP of the same image.
Much is made by some of the "lossless compression" claimed for some other foramts like png and tiff, but those just throw away a significant part of the original information the first time you save in that format, and if you edit the image and make a new save in the same format it's a new "creation" with additional image information discarded, so there's little real advantage of these if you're going to do much manipulation of the images.
Managing your files so that you always have an unchanged original is a lot more critical than worrying about what "perfect format" to use, since there isn't a format that's "perfect" for all uses.