He can take his time adding quality pounds. He was playing at 265 lbs as a true freshman, and adding 10-15 lbs in the off season is a good, healthy pace.
I remember his old man coming in as a 235 lb linebacker as a true freshman, busting his butt to get to 255 lbs as a true sophomore (and that 255 lbs was being generous), seizing the starting NT spot after George "Boo" Williams got booted off the team. He was our best d-lineman, even being badly undersized. It wasn't until 1992, when he was finally at 275 lbs, that he could truly wreak havoc, since he also had Jim Flanigan to help out.
The question is whether Bryce Young plays strong side DE, or weak side DE, since he could thrive at either. It's a nice quandry to have.