npc_citizen_auto_player_squad 1 All these are tested and confirmed to work.
It doesnt always work though, sometimes you have to enable the auto squad feature with this command to get them to follow you. Also would like to note about NPC_citizens, you can get them to follow you on any map, by spawning them in and making sure notarget is off. I haven't tested all of the weapon combinations and I'm pretty sure Zombies aren't going to equip RPG's, so use this at your own risk.
YES NOcreate all npcs with shotguns as there weapons.