You know, I really think that Katara's personality would be more pronounced in a relationship with Zuko than one with A.ang. Let me explain;
One of the most common things people say about the Ka/taang dynamic is that A.ang helps Katara have fun. So basically, it's like Katara is the too serious girl who needs A.ang to help her have fun and bring her out of her shell. There's nothing wrong with this dynamic but I don't think it's really accurate to Katara.
I mean yes, Katara is very responsible, relatively mature and focused, but I don't think the trope of needing someone to help her have fun fits her, I think it fits Zuko more. I don't think a lot of people stop to think about why Katara doesn't have fun much, it's not really because she doesn't know how to or because she needs to be brought out of her shell, it's because she's mostly stuck playing the adult in the room and taking care of things no one else wants to or can take care of. This then makes her look "too serious" many times in comparison. This is why when she talks about the kind of romance she wants, she doesn't say she wants someone to help her have fun, she says she wants someone to lean on.
Katara is an extrovert, she's social and Iikes meeting and connecting with new people
And she knows when to take a break and have fun.
In Zutara, Katara is the fun one, she's the one pulling Zuko to dance with her when he's hesitant, she'd be the one organizing social events and surprise parties, she'd be the one reminding Zuko that they need a vacation, teasing Zuko would be her love language. Zuko and Katara have that extroverted girl x introverted guy dynamic (which I absolutely love, if you can't already tell :))
Think Jin and Zuko except Zuko would be more comfortable with Katara since there'd be nothing to hide and he has a stronger bond with her. It doesn't surprise me that Zuko's date was written by Katie Matilla, a Zutara shipper. Zuko is reserved, he's the character that needs other characters to help him have fun and take a break. From Uncle Iroh to Jin to the entire Team Avatar, these characters do help Zuko relax and have a little fun and when Zuko's around fun people, post-redemption, he's actually quite open to participating-unless if there are more pressing matters at hand-especially if it makes them happy. Like how he tries to make jokes with the team or his little banter with Sokka in The Boiling Rock.
Zuko and Katara have the same level of responsibility, maturity and focus, so no one ever feels like they're parenting or babysitting the other, but their differences are perfect if you ask me. Katara's love would be more openly expressive, more bright while Zuko's way of showing love is more subtle but very tender and thoughtful.
Like trying to make Iroh's tea just the way he likes it and serving him, risking exposing his identity to make Jin happy
boosting A.ang's self-esteem when he seems insecure in the Firebending Masters, trying to cheer Sokka up when he's losing hope in the Boiling rock and where do I even start with Katara, the entire crystal catacombs scene, the entire Southern raiders episode, especially packing all their stuff and telling her to get some rest (There's a list of all the stuff he did in this post I made), that smile when he sees her 🤧 Heck, he even tries with Mai in The Beach by bringing her things in hopes they'll please her.
I love the dynamic of Katara's more bright, expressive and affectionate love with Zuko's more quiet, tender and thoughtful love. I also think his more introverted and reserved way of caring makes Katara feel emotionally comfortable.
Like in the crystal catacombs, he remains patient with her, let's her vent and just listens to what she's saying regardless of her angry tone. He interjects once when she unknowingly insults Iroh but other than that he just listens. She starts to cry and he ignores all the yelling and tries to sympathize with her instead. He then tries to connect with her by being vulnerable with her. He does every single thing right in this scene and his approach not only makes her calm down but even has her apologizing for yelling at a guy who's been her enemy for two seasons.
There's also The Southern Raiders, where despite how angry she is at him, Katara feels comfortable enough to open up to Zuko about the day her mother was murdered, and completely unprompted too.
This post by @allnewalldifferentwildspider also talks about how Zuko's empathy helps him pick up on what others are thinking or feeling.
Zuko is very emotional and passionate person. As much as he tried to hide it to appease his father, Zuko does want to open up and connect with people. Unfortunately, aside from his uncle, most of the other people he knows are like Zhao and Azula. Not the most understanding of crowds. But because of this he can pick up what people are really thinking and feeling. Think of it as a defense mechanism he developed growing up around people like Azula.
Something similar happens during The Southern Raiders. Zuko figures out that Katara is taking out her anger of being separated from her father by The Fire Nation onto him and even connecting her mother's death to him.
It's not the first time Zuko has done this either. He easily figured out that Sokka was planning on going to The Boiling Rock. He does it again during Sozin's Comet when he tells Katara that Aang needs to figure out what to do about Ozai by himself.
I think both Katara and Zuko shine in Zutara but in different ways. But like in The Headband for example, Katara is portrayed as shy, hesitant and needing to be brought out of her shell, even though she's never been shy about anything before and is more confident in herself than A.ang. Yes, A.ang is childlike but Katara is more self-confident. She's the one who tends to his insecurities, who advocates for him as the Avatar and whose been making public speeches from as early as season one. When I was doing research for Katara's personality type in a previous post I made, I found some sites where they genuinely mistook Katara for an introvert, likely due to her portrayal in the comics and LOK.
This extroverted girl x introverted guy dynamic is especially evident in Zutara fanart (Here's some of my favorites, one, two, three and four). I really do think that Katara's extroverted and fun side would come out a lot more in Zutara since she doesn't mother Zuko, she can lean on him, since besides her, he's the most responsible person in Team Avatar, she deeply trusts him, she's emotionally comfortable around him and likes to tease him.
This dynamic they have is also one of the reasons why I would've loved a part two to the Southern Raiders where Katara helps Zuko find his mum. The trip would be more light-hearted since the last one was emotionally heavy (as it should be). I think this trip would probably showcase the funnest and most teenage side of Katara that we've ever seen for all the factors I mentioned in the previous paragraph.