With a DSLR camera, the time it takes to page through documents is the limit on your scanning speed. Paging through by hand, 2 seconds per page is about as fast as you can get. Scanning full-sized papers actually isn’t much faster than scanning film negatives. And definitely for film negatives, most people will want to page through by hand rather than using some very expensive machine that may still come with a greater risk of damage to the negatives.
As for paper documents, you may go faster with an automatic document feed. Of course, the risk assessment is up to you, whether you are okay risking damage to the documents when they run through the ADF at speed, versus slower but safer paging through by hand.