For Hellens and Romans, I'd suggest the infantry units are pretty much on a 1:1 scale to actual units. Polybian legionary units e.g. weren't much bigger than 60 soldiers, while phalanxes I believe were lined up in Seleukid armies in blocks of 16*16=256. Velites and accensi units with half the amount of soldiers into them as legionary Polybians seems realistic as well, given they were only lined up in 6 (instead of 12) rows. (I have this info from Montvert, The Seleucid Army, which might contradict other sources though.) However, during Polybian times, the size of legions and of Seleucid phalanxes greatly increased, perhaps even doubled. I can't remember whether that meant more soldiers in a Polybian principes unit or more principes units.

The scale of armies on the other hand would be much bigger. The AS is known to have field as much as 16.000 soldiers at Magnesia, which is impossible to achieve due to RTW-limits (and possibly due to the limits of your pc as well). Several elite cavalry units in the Seleucid empire seems to have been little more than 1000 cavalrymen strong. The cataphracts e.g. only numbered 1500 men. This should also give you an idea of the ratio cavalry-infantry in those armies. :)

kind regards,

Andy