Astfgl posted:

Each limb has its own health gauge (as do yours, if you check your pipboy) and when you deplete the health gauge you "cripple" the limb. You'll be able to see how healthy an enemy's limbs are while you're in VATS, so it's really not hard to cripple limbs with a gun vs. grenades. Stronger enemies will have much stronger limbs (like Super Mutant Masters, Deathclaws, Yao Guai, etc.) so it's best to focus on the head (for damage) or the torso (for accuracy) to bring them down quickly instead of on the other limbs. There are different benefits to taking out each limb, but as you've noticed these will rarely help you kill the enemy quicker:
- Arms: If you take out the arm an enemy is using to hold his weapon, he'll drop the weapon. If he still has another good arm, he'll usually pick up the weapon with his other arm and start firing again, but you can run and grab it if you're quick enough.
- Legs: Some enemies, most notably deathclaws, will rush you and start dealing massive amounts of damage. If you can take out one or more of their legs from a distance, they'll take much longer while running at you.
- Weapons: Most melee weapons and guns carried by enemies can be shot by you and their conditions depleted to the point of unusability. They'll be dropped and picked up again by the enemies, but since their condition is at 0 they'll be unusuable. Much better than crippling arms if your intent is to disarm an enemy.
- Tongues, Stingers, Antennae etc.: Some enemies like radscorpions, ants and centaurs will have damage-dealing appendages you can shoot. This will either frenzy the monster (like with ants) or prevent them from using that appendage to hurt you (like with centaurs).
- Torso: No real benefit to crippling this, but in most encounters this'll be the easiest to shoot.
- Head: Crippling the head usually outright kills the creature, but when it doesn't it makes it harder for the enemy to hit you accurately. Pointless with helmeted creatures unless you have a good weapon, lots of ammo and you can take a few bullets.

As far as useless perks go, the experience bonus from Swift Learner isn't that great since XP is pretty plentiful. Child at Heart is used about a half-dozen times in the game in special dialogue options, so there are certainly more useful perks to choose. The Lawbringer/Contract Killer perk is handy for making cash, but not much beyond that. Infiltrator lets you pick broken locks, but if you're breaking locks, you're doing something wrong. Same with the Computer Whiz perk, which lets you hack locked-out terminals--if you're locking yourself out of terminals you're doing something wrong.