Just joshin' backatcha, Steel Horse.
Just like real Cowboys can spot a Drugstore Cowboy from across the street, I can spot a wanna-be 'play soldier'. The way they stand, handle their firearms, general deportment. Wanna-bees look wooden, stiff and ill at ease, like they were wearing someone else's clothes.
Their mannerisms regarding superiors and subordinates is another give away. Being comfortable with command only comes from experience. It's easier to portray an Officer as opposed to a Sr. NCO. It is expected that Officers will appear to be unable to find their own butts with both hands, twice on the same day .... ;>)
Sr. NCOs run every army in the world and must give the impression of being in control. Without this stabilizing effect, discipline goes to hell in a hand cart.
Best role by far is that of the common soldier. He can be smartly efficient or the typical yard bird and he can fit into any unit but the crack drill team.
A Royal Engineer associate is a practicing lawyer and has a 2nd degree in history. He chooses to portray a Sapper rather than a highly educated Officer of Engineers. Why? No pressure to fit into the mould of a Victorian Officer and Gentleman.