i think they’ll age throughout the series, but not so much that he’ll be as old as claudus. i think by the end they’ll all look different than when they began. panthro losing his arms was the first step in their physical changes.
Leopards are quite a way off being the strongest of the cats, they are one of the smallest members of the ‘big cat family’, and in order of strength of big cats it would look a bit like this:
[ol]
[li]Tiger[/li][li]Lion[/li][li]Jaguar[/li][li]Leopard (all variants e.g panther, snow leapoard, clouded leaopard)[/li][li]Cheetah (taller but not as muscular)[/li][/ol]
It’s a bit of a mystery why Panthro (presumably based on a Panther) is the strongest, but as some1 said, we shouldn’t look too much into it really.