Unique NPC "Giant" is the best. DLC unique NPC "Little and Nickel" are second best. All the others have growth rate similar to male natives. But with enough training, they will grow stronger.Is there a way to make female npcs decent guards/combatants? I want to have my base guarded with my war harem.
Weapons are a problem. Pretty much nobody except the two MCs can wield decent weapons.
People often recommend giving them bows. Bows aren't very powerful, but they can strike enemies stuck outside due to horrible pathfinding or fighting your rabbit meat shields.
Elder Sister natives can wield spears, which are moderately powerful. You can also have mummies defend the gates - I'm not sure if they are actually powerful, but you can easily get them at moderately high level they are in the dungeon.
Consider weapons you get from Halloween raids. And those from elite raiders. They're better than ordinary stuff natives carry.