His defensive game is already pretty strong for his age, but yes definitely catch him live if you haven't - he's got good top end speed and plays with a cleverness, especially in finding goal scoring spots, that backs up the production he's had lately.
I don't think his physical maturity should be a knock against him. He obviously uses that to his advantage at the junior level, but lots of top prospects every year are physically mature or ahead of the curve.
He's easily a Top 5 talent that we've ever had in Owen Sound and all of the other have gone on to at least play in the NHL (Bobby Ryan, Nick Suzuki, Joey Hishon). Barlow might be better at 17 than all of them.
Even if he topped out as a middle six winger, that's still a good use of a mid-first round pick, and his shot and defensive game suggests he should slot somewhere into an NHL lineup.