One of the things that always sticks out to me as “pro quality” are those huge, hanging triceps, versus a flatter, more of a “straight line” kind of shape. You can see it above on on the Flex and Priest shot… Obviously Flex is the best in the world as what he does so this is certainly not me knocking the guy, but Flex’s triceps dont have that “hang” shape that Lee’s do in spades… Just watching him in that video you can see the sheer mass of that tricep.
Aside from things we CAN change like overall size and conditioning, this is really just one of those things I really think you either have or you dont.
This and a crazily developed, and again “hanging,” hamstring are 2 of the more noticeable body parts on someone who stands out to me.