Yes, check my "ENDURANCE - the real deal " thread. There is some insight in there.
To get a chance at a rare baby (28 SPECIAL points), you need a minimum combined SPECIAL (dad + mom) of 122.
To get a chance for a legendary baby (40 SPECIAL points), the combined SPECIAL of the parents needs to be at least 134.
Getting a specific SPECIAL of the baby to be the highest at birth is somewhat difficult.
The method I used was to breed 2 dwellers that each have a 10-10-10-9-9-10-10 as their SPECIAL. This results in a 50% chance that the baby will have an ENDURANCE spec, and a 50% chance for a LUCK spec.
The babies will still be born with 105HP, no matter what their endurance is, and have no special bonuses that I've noticed. The only real advantage of a rare or legendary baby is less training time needed to max them out.
Also, the parents don't have to be legendary (lunchbox) dwellers. They can just be regular folks with high SPECIAL.
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Armor:
As far as the armor type goes, only the actual stats matter. Power Armor will work the same as leather armor with the same stats.
The best you can hope for is to take 2 damage from winning an encounter with a higher level enemy. I have not seen a way to reduce this at all.
Boosting stats by armor works both inside the vault and outside in the wasteland.
Boosted LUCK in the wasteland gives you more caps, and more chances at picking up an item. In the vault, it decreases the rush failure percentage, and increases the chance and amount of caps you can get when you collect the resources from the room that dweller is working in.
Boosted ENDURANCE increases how much HP your dweller gains when going up a level, so if they are less than level 50, give them the best endurance gear you have and make sure they are trained to 10 endurance. This is the only way HP increases.
Boosting other stats like agility and strength help to determine if you will win a specific enemy encounter in the wasteland. In the vault, the boosted stat will decrease the time to complete generating the resource from the room the dweller is working in.
You need 11 endurance to get NO radiation in the wasteland.