The Qcup regulars will be able to answer better than me, but I'd say he looks to have an elite short kicking game and his 2024 qcup to win halfback of the year was apparently pretty dominant with him being the stand-up choice to win it.
So I think he's got the fundamental skills as a halfback.
I think his issue at cows was defence (he's got a slight build) and his long kicking may not be as long as you'd like (from memory but haven't seen enough of his game to remember).
He was the front runner at cows all through the preseason, but they said he could go I think after Dearden played well in origin?
He was dropped earlier than that to bring Clifford in, but after Dearden played 7 at origin they tried Dearden 7 with Purdue at 6... I think Purdue in the halves failed for the most part and they went back to Cliff... but ultimately it seems like those 3 were the ones selected as their halves moving forward... and Duffy was told he can look elsewhere, mostly because Dearden is earmarked as their 7 moving forward.
In terms of defence and long kicking I feel like both of those things get better over time as you do more preseasons and do more weights, more experience, etc.
Reyno isn't exactly built or putting shots on, but his tackle efficiency is like 90% over the course of his career... so Duffy will have a great mentor to learn from if defence and long kicking are his biggest things to fix