These are the limits for cncnet (taken from spawn.xdp)
For singleplayer you'll have to check rules.ini
; ******* Object Heap Maximums *******
; These are the absolute maximum number of these object types
; allowed in the game (at any one time).
[Maximums]
Players=8 ; ipx layer limits this to 8 maximum
Aircraft=150
Anim=100
Building=650
Bullet=50
Factory=32 ; 32 is minimum for 8 player game
Infantry=550
Overlay=1 ; special case -- only needs one
Projectile=20 ; projectile types, not actual projectiles
Smudge=1 ; special case -- only needs one
Team=60
TeamType=60
Template=1 ; special case -- only needs one
Terrain=500 ; trees and rocks
TrigType=80 ; trigger types
Trigger=200 ; triggers themselves
Unit=650
Vessel=150
Warhead=10 ; warhead types, not actual warheads
Weapon=55 ; weapon types, not actual weapons