Let's Find Those Trait Improvements

Heads up! The Sims team has shared those improvements.
Here's the link: https://forums.thesims.com/en_US/discussion/989333/sims-411-recap-inside-maxis-27th-april-2021#latest

I'll quote (and format) it here.

What personality traits were updated in the last patch?

Bookworm
Bookworm Sims will prefer to choose reading activities autonomously over other Fun actions.
NPC Bookworm Sims will be seen carrying books where possible.

Cheerful
When a Cheerful Sim socializes with a non-Cheerful / non-happy Sim, that Sim has the chance to get a Tense 'Cheered to Death' buff.
Cheerful Sims will autonomously try and perk up Gloomy Sims
Negative emotional buffs will decay faster than usual when Cheerful Sims are in a Happy mood.
Cheerful Sims have a greater chance of success with Friendly socials when in a Happy mood.

Clumsy
Clumsy Sims have a chance of failure when engaging in sporting activities like Using a Treadmill, Ice Skating, Snowboarding or Skiing.
Clumsy Sims have a chance of stumbling when walking around - this will elicit a response from nearby Sims.
Clumsy Sims with higher Handiness have a lesser chance of breaking objects.
Clumsy Sims have a small additional chance of breaking certain electronic devices like the Computer, Research Machine, Juice Fizzer, Cupcake Machine, Games Console, Arcade Machine and Popcorn Maker.

Genius
Genius Sims have a chance of a 'Eureka Moment' while showering or bathing that gives a small amount of skill for a random skill they already have,
Genius Sims get a new interaction 'Solve Hard Problems' that helps them build Logic skill.
Genius Sims get a new idle where they appear to be pondering / solving problems.
Genius Sims will prefer 'cerebral' activities like Chess over other more trivial Fun actions.

Gloomy
Gloomy Sims will choose to autonomously Mourn, or act in a gloomy way (like sighing to themselves) more often.
Gloomy Sims will get an Inspired 'Spectral Influence' buff when in proximity to Ghosts.
Gloomy Sims get Sad moods prolonged if they see Cheerful Sims doing cheerful things, and also react in disgust.
Gloomy Sims have an increased chance of waking up in a Sad mood.

Glutton
Glutton Sims will autonomously choose to grab snacks more often.

Good
Good Sims get a new interaction 'Help Out' that reduces negative mood duration on another Sim in a negative mood.
Good Sims have a lower chance of choosing to do Mean or Mischief actions autonomously.
Good Sims will autonomously choose to react negatively to seeing Mean actions being performed.
Good Sims are more likely to choose to do Friendly actions autonomously.

Goofball
Goofball Sims are more likely to autonomously choose Mischief or prank activities like Prank Toilet.

Hates Children
Asking a Hates Children Sim to 'Try For Baby' has no chance of success unless the Sim is Dazed.
Hates Children Sims will get Tense, then Angry around child Sims, and also move away when they get to the Angry stage,
Hates Children Sims will look annoyed when idling in the Tense or Angry buff stages.
Hates Children Sims get a Happy 'Quiet Environment Child-free Zone' buff if away from children for a time.

Hot Headed
Hot Headed Sims who get pranked have a greater chance of getting Angry.
Having other Sims Enthuse about things can make Hot Headed Sims Angry.
Hot Headed Sims get Angry if they lose career performance
Hot Headed Sims won't be targeted by other Sims as for Mischief actions.
Hot Headed Sims get Angry at failed romance attempts (giving or receiving).

Jealous
Jealous Sims get a new interaction "Talk through issues" which gives a chance of a reduced duration of negative Buffs from less serious Jealous buffs
Jealous Sims get a reduction in the duration of less serious Jealous buffs
Jealous Sims are now less sensitive to time spent away from their SO.

Mean
Mean Sims will autonomously laugh at other Sims misfortune.
Mean Sims are more likely to choose to do Mean actions (like Kick Over Trash Can) autonomously.

Neat
Neat Sims are more likely to autonomously choose to do cleaning actions more frequently.
Neat Sims will try and clean things that aren't dirty autonomously.

Noncommittal
Asking a Noncommittal Sim to 'Try For Baby' has a very low chance of success.

Perfectionist
Perfectionist Sims will get an increased chance of Masterclass crafted objects, and will react favorably when they do.
Perfectionist Sims may choose to autonomously repeat some crafting actions (like Painting) numerous times.
Perfectionist Sims who create any Masterwork have a high chance of gaining a Focused ‘In The Zone’ buff which has a chance to increase the quality of another crafting interaction.
If they do achieve a better quality during this buff, they gain an Inspired ‘Focused Payoff' buff.

Ambitious
Ambitious Sims will autonomously mock Goofball Sims for Goofball actions.

Slob
Slob Sims will autonomously mock Neat Sims for cleaning things.