CSFM uses a combination of various AI mods like xStream AI and Bak aka Rulix AI in order to improve Human NPC AI. Here's a brief explanion of what each scheme does improve in AI:
Medic Scheme (xrs_medic)
In this medic scheme, NPC's are able to heal them self (with bandages and medkits) and heal their fellow wounded stalkers.
Grenadier Scheme (xrs_grenade)
In this Grenadier scheme, NPC's are able to throw grenades upon their enemies.
"Outfit Dress" Scheme (xrs_armor)
This scheme make NPC's be able to upgrade them self with suits that they can loot from the ground or outfits that player trade to them. From time to time, NPC's will auto-upgrade their "outfits" without player give him a suit or loot it from the ground.
Body Looting and Item looting Scheme (watcher_act)
Basicily this scheme make that NPC be able to loot bodies and get items that are on the ground.
"Facer" Scheme (rx_facer)
In this scheme, NPC's will be able to melee enemies that are close enough to the npc.
Friend Fire Line Scheme (rx_ff)
This scheme makes the NPC's change position if a neutral\friend stalker is in his firing line.
Weapons addons Scheme (rx_addons)
This Scheme makes the NPC be able to attach weapons addons (silencers, scopes, grenade launchers) to their weapons.
Grenade Launcher Scheme (rx_gl)
This scheme will make NPC's use grenade launchers.
Stalker are not blind scheme (anomaly_holder, anomaly_evader)
This scheme will make NPC try to avoid anomalies with or without sucess.
The NPC weapon chosing is managed by some changes in the weapon files.
Red 75 NPC Cooperation scheme (actor_need_help)
Well, this is a scheme that let the player (you) be able to hire stalkers to fight in your side (It works like a companion mod). In order to hire a stalker, you need to be achive a friend status with the NPC (By helping them with a fight, healing them when wounded, doing quests that improve your relation with a faction or simply join to a faction)