The NFL stat.s people started recording the speed of players while carrying the ball in 2018.
According to Yahoo Sports, the players who have hit 20mph/32.2kmh the most since then are:
T Hill: 73 times - not unexpected given he is known for his speed, although the 73 total may be a little more than expected
D Henry: 27 times - yes, he's only behind Hill, although a long way behind
The numbers are obviously dependent upon starts and useage but, even so, I an surprised Henry is 2nd.
He is mostly known for running over people, not out-pacing them.
Given he is 74 inch/188 cm tall and 247lb/112kg the running over people is not surprising. He's built.
The speed is surprising - to me, at least.
The fastest NFL player: D K Metcalf at 22.3 mph/35.9 kmh
The AFL has been tracking speeds since 2017.
The top speeds: 37.8 kmh: G Rohan, C Comben; 37.4 kmh: O Markov
As the top speeds of the AFL players aren't limited to when a player is carrying the ball you can't really say that they are faster.