All athletes mature/reach their peaks at different rates, but you can certainly generalise in respect to when 'most' athletes in a certain sport hit their peak.
The East Germans and other countries behind the iron curtain certainly studied and enforced who could do which sports based of physical attributes, age etc.back in the 50's and 60's. They even had blokes running around in ladies events, they were that good at it. All in the goal of cleaning up medals at the Olympics.
Swimmers and gymnasts often hit their peak in their late teens - early 20's as opposed to distance runners and cyclists who often peak in their mid 30's.
Personally, I don't think most forwards would hit their physical peak until at least mid 20's. A classic example is Petero Civ, who I don't think really hit his peak till his early 30's.
I think Bryce has all the skills to go on and be one of our all time best forwards, but personally, I think he needs to play the game a bit tougher. He needs more aggression in his defence, and sometimes he just needs to charge at the line and not even think about an offload. A bit of time in NSW cup would probably be good for his confidence. He would absolutely dominate at that level. He's probably a few years off hitting his physical peak.