So the EFA (Who I'm assuming are the Remnants) in OFP are regarded as a bunch of low skill farmers, who have limited military experience, which we learn that the majority of the commanders are killed when we went back to Everon.

The Remnants are able to launch complex ambushes, while the AI for the US and Soviet forces exception of at the main base, are just standing around doing nothing aside from looking 360 and turning on the spot.

This shouldn't be the case, since they are a militia level formation they shouldn't have as high of a skill level in comparison to the US and Soviet Forces who both sides forces went through basic training, and advanced training for their roles (Mind you I know the Soviets were less trained and more reliant on manpower than the NATO forces were).

The Remnants AI, can also spot and shoot you perfectly from one shot going over their head. In reality it takes more than one shot to figure out where an enemy is, especially if they are in a field crouched into it with only their head visible at 300+ meters.

But even a soldier assigned to do base defense, would be better trained than a paramilitary formation (Unless it's private contractors which we have no evidence of the ESA/Remnants being PMC's)