In the Galacticraft let's play, Mirror (Zero) is unfamiliar with the mod, while Sol (Max) is the smart one. Max has been known to be a fan of Achievement Hunter, who did a let's play of Galacticraft not long before Max started his, so it's likely that's where he picked up the knowledge.
In the first episode of Resident Evil 5, Dan is the first one to die and Max keeps running out of ammo (and having poor aim with his weapons). Near the start of the episode, they both read in-game documents containing game instructions; Dan reads how to use firearms, and Max reads how one can come back from the "dying" state. The Fridge Brilliance kicks in when you realize they didn't read the documents the other one read.
Why do Mirror and Sol hang out so often when it's clear Mirror doesn't like Sol? Mirror is part changeling, and so would feed on love; Sol is part windigo, and so would feed on hatred. So Mirror would get a good supply of positive feelings from Sol, who would get a good amount of negative feelings from Mirror. It's less liking each other and more just tolerating for the sake of mutual benefit.
Actually, conversation implies they're agents working for Princess Celestia, so they're forced to work together.
Max's first let's play was The Legend of Zelda: Ocarina of Time back when he was twelve to thirteen years old; as such, he was childish, bad at jokes, bad at gameplay, rambled on, and everything was of much lower production quality. Almost a full five years later, he started playing The Legend of Zelda: Twilight Princess. Due to developing his personality over those years, he's now snarky, competent, is quieter when need be, and everything is of much higher quality. Twilight Princess comes after (though not immediately after) Ocarina of Time in the Zelda timeline. Max has literally become Future Max.
It also helps if you know about the true identity of the Hero's Shade.
When Max gives his Catchphrase, "What am I fighting fooooor?!", if Zero's around, he'll sometimes gruffly claim that's his line, even though he's rarely if ever said it. Think about it, though - in that line's origin, what was the name of the character who said it?
Max has said a few times that he didn't grow up watching a lot of TV, only really remembering Kim Possible and Pokémon: The Series. That's carried over to present day, where he still doesn't watch a lot of TV, meaning he doesn't get a lot of pop culture references.
Max loves games such as Stardew Valley and romantic visual novels, which are primarily meant for immersion, and he always "roleplays" in games like Fallout 3 by choosing actions and dialogue that best fits him instead of goofing around. Yet when doing the Undertale genocide run, which is specifically made to make you feel bad for killing these characters, he shows no negative reactions and has mentioned on Twitter that "it's just a game". It probably lost its appeal to him since he had to play the game twice (because he couldn't get the True Pacifist run chained off his Neutral one due to killing some monsters), so the immersion was broken and he just saw genocide as a way to wrap it up.
Not only is Max typically the Dungeon Master for the group's Courage is Magic sessions, he makes up literally everything on the spot outside of a very basic outline. He took improv classes for years and has been let's playing for about half a decade; his mental reaction time is amazingly swift as a result, so of course he can create the pieces of his campaign as it goes along rather than beforehand.
He's also The Workaholic and might not have time to prepare a full series of quests, so he does it live.
When Max goes to Ten Carat Hill to catch a Rockruff, he's noticeably unnerved and mentions being on edge. Ten Carat Hill, in the postgame, is where you find Necrozma, and it's implied that it's still there even before you can encounter it, you just don't run into it. Obviously wasn't the idea, but it's fitting.
He also mentions the area making him think a Burrowing Snagret is going to pop out at him, which at first sounds like a bit of snark, but think about it. Ten Carat Hill's meadow is a pathway leading to a large circular area (though also has not-immediately-visible paths and grasses branching off to the side). It genuinely looks like a boss arena at first with said boss absent, and Pikmin is a game series known for having no buildup to boss battles, just tossing them at you often with a Jump Scare as they either pop out of the ground or fall from the sky. Jumpscares are one of Max's biggest fears; no wonder he felt so on edge!
This also explains his extreme hesitance to fight Stone Talus, since all Tim tells him about it is that it "comes up from the ground".
Max is anywhere from unnerved to scared of: water, space, darkness, underground/caves, things he can't make out from a distance, and wide-open areas where he's not entirely convinced everything has loaded in. He doesn't have a bunch of specific fears; he's just afraid of the unknown!* Though it's worth noting that some aspects of his aquaphobia are unrelated to the "unknown" part of it.
Max and Rhino are good friends, yet constantly argue. Max likes to improvise and take risks for quick progress, while Rhino tries to plan everything out and go carefully for safe progress. Naturally, when both try to lead one another, or work together at all, these contrast.
Max doesn't do well using characters or weapons that are Difficult, but Awesome, but also hates Boring, but Practical. The former is because Max rarely does well under pressure, and so likely wouldn't remember all the complex properties of his abilities or weapons. The latter is because Max used to always be the only person recording (and even nowadays is sometimes the only one doing so) and he didn't want the audience's experience to be dull; over time it just became ingrained in him that he disliked those roles.
The last part above also explains why, despite his surprising skill with sniping (see The Legend of Zelda: Twilight Princess, Minecraft, and after a time, The Legend of Zelda: Breath of the Wild), he avoids it when possible; doing sniping yourself is an exercise in patience, caution, and timing, but when you're watching it it's a lot more boring.
Max's biggest criticisms in games tend to be of plotholes or bad dialogue. His main focus when being a Dungeon Master is the story and narrative. He's quick to think of wordplays and puns. His snarkiness often comes with a helping of Sophisticated as Hell. And he's good at noticing suspicious things in text or speech, which he keeps in mind asforeshadowing. All seems a bit random; then you remember that Max's biggest and most consistent hobby, outside of making videos and playing games, is writing.
The intro to the final episode of Minecraft Hardcore season 2 features the song "Bad Luck Charm". With his Survivor Guilt and The Atoner tendencies as the series went on, it suddenly becomes clear that the song is (in this case) talking about Max.
Also, the lyrics when each death is shown line up rather well with the death themselves:
"Pain; is your reward for being near me" -Endorb's death, which was stated earlier to be extra painful if it happened due to him being a newcomer to the channel.
"Fate; won't be your friend when I'm around" -Rhino's death, which was caused by a fateful glitch the players had no real control over.
"Blame; me for the tragedies that follow" -Tim's death, which Jero vehemently blamed Max for.
"Grave; the situations that surround" -Peter's death, which happened due to him throwing himself into a gravely dangerous situation rather than backing off.
