The biggest concern for Williams and Carter is adjusted college competition. Many of the ACC defenses were bad, which could lead to over-rating. Williams broken tackle rate is amazing.On top of this positive outlook, there has also been a strong correlation towards running backs drafted that were traded up for by the team to acquire.
JJ Zachariason has a reference in his rookie rankings on number fire.
https://www.numberfire.com/nfl/news/37804/zachariason-post-draft-fantasy-football-rookie-rankings