Note: Not a full formatted chapter. I'm kinda tired and depressed right now, not doing so hot, feel really insecure about my writing, that kind of depressed. But here's the chapter draft.
I have two favorite tropes.
One: we discover that our first person protagonist, who we assumed is the default normal person, is actually seen as the abnormal one by other people. I don't mean "everyone secretly knows that Bruce Wayne is Batman but pretends not to for some reason." I mean, "we've been following Holden Caulfield around and he's very judgmental of other people but it turns out he's a total wimp who loses every fight he gets into and also everyone secretly thinks he's gay but he has no idea."
A character who will occasionally trip on something or who the readers know is a bit of an airhead, and insists these things happen because they are dumb. Yet, they get invited to make a speech as valedictorian and are told they have to leave their class and enter a gifted class, which becomes a subplot when they try to avoid both of these things.
A character who is very judgmental of other people and sees them as inferior, but rarely gets called back after auditions/gets lost a lot, more than is normal for an average person/gets beat up a lot/is such a prude that they have also been a virgin for longer than most of their nonconformist sheeple friends (who actually had sex and got tattoos and got drunk before they became boring nuclear families, since that's a perfectly normal procession of life events).
A relatable protagonist with very ordinary struggles who is actually really rich and doesn't even realize it (aka Rebecca Bunch)/ Or maybe they don't brag about their label stuff, but they don't understand why someone needs to work more than one job and they casually buy an expensive bag just cause it looked nice without really thinking about the price or label.
My second favorite trope is when we discover something about a secondary/side character which makes them somewhat more of a real person. I don't mean "we find out that the Joker has a secret lover and a secret goddaughter who he abuses." No, we know the Joker is a shady guy and we'd totally expect that from him. I mean more like, "Batman actually had asthma when he was younger, like he used to use an inhaler and he sometimes stops in the middle of a chase because he needs a second to check his breathing, then will start chasing again, and that's why he pauses dramatically sometimes confusing other people." Facts that you could learn about someone living right next to that would be cool.
I don't mean these secrets are supposed to gain them sympathy. Let the character types deal with their secrets the way their personalities dictate they would.
Arrogant characters get annoyed at the thought of something getting in their way and grumble and curse at their obstacles, while unabashedly gloating their superiority in the fields that they have no difficulty with.
For example, this character who memorizes tons of facts about obscure historical figures and bragging about their PhD in History who has dyscalculia. When the bill comes out, they just stare at it and are puzzled, and someone nicer has to volunteer to calculate it for them. They just look uncomfortable and don't say anything about the bill. People assume it's cause they're cheap and don't want to pay their share, but they just genuinely have too much trouble trying to calculate it. After a while, they just kinda accept this is how they are and when the usual nice person is out, someone else will help them calculate the tip.
A character who is a really rowdy (but feared) shounen protagonist fighter actually has trouble navigating because they can't read the signs due to dyslexia. They don't actually know this, they just get mad when other people mock them for the stereotype that all fighters are illiterate jocks, but it turns out they just had a learning disability and decide to retake reading lessons at a children's school/have a wizard cast a spell on them to facilitate reading. The other characters pitch in and help read stuff aloud to them.
A character who everyone thinks to talk about themselves but actually can't stand being in large social settings because of the overstimulation from conversation. They don't show up to large social gatherings, or they do show up and always seem a lot more reserved than when they're with the group traveling.
A character who actually has allergies. They get really upset because the meal had peanuts in it, then leave and come back. The group doesn't understand why they were so prissy about it, but actually they just barfed it up and were too proud to ask for help or let others see them in a weak state, so they just act annoyed and tell others to be more careful next time.
A character who is surprised to find other people can afford to not use a wheelchair without sacrificing a lot of energy. They're very mad and insist that this is the norm, but others say that's not their situation.
A character who is a known genius has horrible spelling/often pronounces certain words oddly (not quite a accent, they just say "rendezvous" like it rhymes with "Ben says mouse") due to their learning disability. They're secretly embarrassed, but everyone laughs it over and finds it endearing.
2. Characters who are very chill and underrated and comfortable being in the background and who put up with the egotistic protagonist's constant bragging are probably going to be extremely modest about their impressive abilities/secret. Therefore, you can just hint at their abilities with minor impressive feats that slip under the radar.
That character with an accent who everyone treats as a token ethnic friend actually has an IQ of 160? Maybe they correct someone (possibly, the arrogant person who is used to dominating and shutting down the argument) on some obscure fact. Or they laugh at jokes that only academics would understand (initially, everyone might assume they just laughed even though they don't understand it cause they're basic like that, but it turns out they actually understand it all along).
Is actually ambidextrous/worked as a jester for a few years? They just casually juggle their sword when bored. Also, can blow balloon animals and comes up with really good jokes to entertain the group.
Used to work as a cook at a soup kitchen/for career purposes? They offer to take the cook's place for one evening and everyone is surprised when the food doesn't suck but is like, really really good.
Has a prosthetic eye/limb? Wait why didn't they mention it before? Eh, it just never came up. Or they didn't find it relevant then, until now that their prosthetic part is lost/stuck/requires external help/they felt like talking about it just now.
Secretly a polyglot? Everyone fusses over how to translate a rune, but they walk over and translate it no problem. Everyone is so relieved they don't even bother asking questions about how they know it and focus on the next step.
A character who actually has an autoimmune disease or diabetes or use antidepressants. Nobody really noticed it cause they're always cheerful but one day they miss their meds and are concerned. Everyone is surprised, but helps them look for them nonetheless.
A character who was always a pleasant friend is gay, and didn't come out even when someone else came out cause they don't really see their sexuality as something particularly unusual.
A character who does a lot of dumb shit yet actually knows a lot of stuff that normal people don't because they graduated from Harvard (again, Rebecca Bunch).
A character who just has super strength (they don't have any difficulty lugging huge weights or they can throw a ball so hard it breaks something, without even trying).