Over a year ago I scanned hundreds of our old paper photos dating back to 1920.
Scanning is laborious so I decided to do it as well as possible so I don't have to do it again. I used Canon CanoScan LiDE 220 to scan at 600ppi with billions of colors as .tif with some extra space around each image (the scanner software allows to rotation which was nice because it is nearly impossible to set some prints straight into the scanner. Some prints were glued to books which required pressing the scanner with the other hand and even then produced some artifacts. I removed some prints from the albums if they were not too tightly glued). Most of the prints were B&W but I scanned in color because it allowed me to fine-tune the B&W final output, if necessary in some images). I named each scan as YYYY-MMDD-mm-ss.tif to the best of my knowledge (sometimes I just guessed and fine-tuned it later by asking relatives and doing some detective work...). I added a code to the end of each filename so I could find the original print fast, if a re-scan was needed.
I then cropped, edited (quite casually whites, blacks, shadows, highlights, contrast etc) and output from Lightroom as .jpg. I let some B&W images remain in color if it looked nice but converted most to B&W.
I then added EXIF date, location, captions, keywords and ratings to the best of my knowledge to the .jpg files and archived them and the scanned .tif files on plain folders on two identical HDDs. I can grab a .tif if I decide to re-edit some scan.
Then I imported the .jpg files to Photos.app, synced them to iOS devices and asked more possible details from relatives etc. I added any extra info to the archived .jpg files and replaced them in the Photos library when there was enough relevant info.
If that sounds like a lot of work ... it was! But the end result was nice and brought the old images back to life. I had done the same to old slides and negatives a few years ago but I then used a cheap 'n fast device for scanning (the main purpose was then to put the images in order and check what the images contained) and I have planned to re-scan the best shots with better quality later.
For photo prints, 300 ppi is fine in general; scan at 600 ppi to make sure you get all the details hidden in your prints. For slides and negatives, 2000 dpi will give you the equivalent of a 6-megapixel photo, which is good enough for most standard print sizes.