I am in complete agreement with Wulfir. Research is the best way to go. For example
If you are playing 1978 US, a Mech Infantry company had 9 Dragons and 2 TOWs. And this does not take into account any of the 12 TOWs in the Combat Support Company.
That gives you 45 ATGMs (not counting 3TOWs the scouts have) in one Battalion.
Some armies will just rain ATGMs on you. The French will do it too.
OTOH What if you are playing Angola or Cuba in 78? certainly they would have only a few if any.
That said, limits are all well and good, but some players try to manipulate the game to their style of play. IE " Lets play 1944 Germans vs US, no air or 2 air......" Then he shows up with a horde of Tigers and Panthers. Or 10% ARTY, no Air, low points, 30 turns. Let me guess, you like infantry........Or "lets use this map" the one with lots of terrain so my FC 3 tanks can sneak up on your FC 15 tanks oh, and no helos...
Buyer beware:)