Definitely not a plodder. Not sure how he would translate vs #1s but a lazy comparison for me is a Peyton Hillis lite player.
Sort of the same usage in college, except Hillis had to fight for touches with McFadden and Jones but he was the punt returner iirc.
Same size, Luepke has a better vert but same 40(4.65 combine Hillis-4.55 Luepke pro day).
He's not a traditional fullback that can just block or fall for a yard or two. Honestly, while he has the size for it, I think he's more of a running back in the NFL but can lineup as a H-back or fullback if need be.
I think if he sticks on the 53 it's due to the team thinking he can play ST's, and go light at first at linebacker(Cox) but also some upside with the ball in his hands. Something that the former fullbacks we've had here since McCarthy been here never really offered.