i also have npc's travel in my load order. that brings random people walking around the commonwealth. some aggressive, some not - its one of the other mods i use to make the commonwealth a little more 'alive'.
these three mods are the ones i use with simsettlements the most as they are trouble-free and once installed and configured, that's it - they just get on with what they are doing.
one other mod i have is true storms, and with that i have ghoul horde chance set to 100, and also set to spawn in settlements, and spawn large mobs. what this does - any time there's a rad storm, i have to find cover. if i am in a settlement, it will be on the end of a ghoul mob, which, tallied with radioactivity in the storm, makes even settlements a dangerous place. you may want to look at that as well.
note; settlement attack system; - depending on how high your defence rating is, it will spawn attackers to suit. so if you go ham on turrets and defence, you can get quite large and well armed enemy patrols that will try and take your settlement apart. if you have mortal settlers, they will die. skk50 has another mod out there which will allow your settlers to use stimpaks automatically. you can give that a look too.
p.s. there is a post in these forums that i made where i was playing conquest and tried to attack tenpines bluff as a raider - at the same time, skk50's settlement attack system spawned in about 30 supermutants, armed to the teeth.
spoiler; we got slaughtered.