He's the signing I'm most excited about, but that's possibly because he's an attacking player. He just has extraordinary potential. I'm not expecting the world from him, but it would surprised me, if in a few years he reached Hazard-like levels.
In terms of his immediate impact, I think the tour will determine whether he starts instantly over Young or not. He's certainly a far more naturally talented and productive player, but LVG might want to initially start the tried and trusted Young which paid dividends for him. He will eventually displace Young either way. It's just a matter of time, as he's simply a better player.