Platoon/Squad Tactics: Your largest unit, the standard rifle platoon will be under 50 men. Most special units will be squad sized (8-12 men) or even smaller. This of course is a big change from the massive armies of TGW, and while battles will not be as large, it does offer possibilities of more tactical approaches to battle that hopefully will reflect the big changes in warfare between ww1 and ww2.
Infantry will be the main component of your army. Small enough to avoid artillery, longer ranges, and better rifles will make these units, while smaller, much more deadly. Special units such as snipers or assault infantry will fill very specific roles, but will be equally vulnerable to attack. However, most infantry units fit a large variety of roles, experimentation is key.
Cavalry was outdated in ww1, and it was definitely outdated in ww2. These units should never be used in a direct confrontation with infantry, as they will be destroyed. They can be used to go outside of the enemy's range, and then attack isolated infantry or artillery from the flanks, or be used as a dragoon role.
Artillery, while no longer the dominating field force as in TGW, still very powerful. No longer can you simply let them shoot wherever, fewer pieces, smaller units, and higher accuracy, will mean more focused targeting. Machine guns however, remain strong as ever. Tanks will also be included hopefully, but this is limited by TGW progress in this area.