My fave traits in the sims 4 used to be slob and gluttony, and i personally think that these were the only two traits that matter than the rest. all traits works the same way (it gives you random moodlet and emotion, you're not doing genius stuff? you're gonna be tense, you havent exercise in a while? you're gonna be tense)
And yes The Sims 3 really nailed it with Traits system, just recently finished my gaming session and in that last lession as soon as my sims get out of the class, the mean spirited sims out of nowhere slapped my sims and then continue to pick a fight.