OWS: These are the standard rank of almost all OTA Soldiers. This stands for "OverWatch Soldier". These Units are not as highly trained as the EOW (Which we will explain next) but understand the full concept and how to deal with almost all situations.
OWSS: While their name does sound a bit Nazi-Like,they are OverWatch Shotgunners. They are a much more aggressive unit with denser kevlar and thicker armour. They are an optional rank and are not needed to get promoted to EOW. They excel in raids.
EOW: These are the Higher ranked units in the OTA Division. This Rank stands for "Elite OverWatch". This means that these Soldiers are practically Un-Human and almost all robot. Their bodies are Heavily-Augmented and are rarely sent out as the OWS mainly do the dirty work.