I did end up testing the extra attack vs Higher level and lower level units, those work fine.
It seems like if you choose Underdog and Brute on your trained troops, they get +3 attack against all units that aren't exactly the same level, thats pretty useful I think. I think they should be mutually exclusive for flavor purposes.
Nah thats ok, they are rather costy too, and I can find you better traits
But thanks anyways, and I wouldn't mind too much if they were exclusive, I never use them anyways.