Practicing Cryptid™

For Benoit Blanc:

First thing's first, he immediately clocks Fifi as completely innocent and makes her his partner in the investigation ala Marta Cabrera. He's really gentle with her regarding Freya's diary, even giving her the option of not opening it for him at all.

He completely skips Poppy's suspicion in its entirety, I highly doubt he'd suspect her as well if he already knows Fifi is innocent.

The ones he suspects most are Pointer, Hawkshaw, and Penny, especially Penny. He would see how she acts regarding Poppy and immediately know something is up with her.

Blanc would end up getting Felix's suspicion first, which would immediately lead into Flora's. After Flora he'd feel even weirder about Penny— she's the only other bird enjoyer on the island.

Getting Penny's suspicion only intensifies it, as it really does feel like something put there to purposefully mislead him. Same with the painted "knife", he would only entertain that possibility in order to play stupid at someone.

He would also realize close to immediately that Penny's testimony doesn't line up with Pointer's. After getting her suspicion he practically knows she did it but is still piecing together how.

He would find the study without needing to go to the Lowest Level. He and Fifi would see everything in there. They would find the crossbow base. They would find the Hawkshaw notes. They would find the inkdip feather in the furnace. Everything they suspected would be confirmed.

They would still get into the Lab and the Lowest Level, specifically because that's what Freya would have wanted. That's when they find the bolt of the crossbow.

Honestly, I would kill to see someone who's really good with writing Blanc write this because the idea of Fifi confronting Penny and getting to scream at her for Freya is so fucking good it makes me want to start chewing my limbs off like a rat in a glue trap

As for Grimoire and Sally:

Neither of them would fall for the Disruptors' pseudo intellectualism. Sally knows when people are simply just stupid and greedy so she would clock it immediately, and Grimoire would not be that far behind her.

Grimoire and Sally are really good at fucking with people and playing stupid, so when they need to buy time for Helen that's exactly what they do to Miles (Grimoire makes a personal effort to piss him off at any conceivable moment and feels good about doing so whenever he succeeds).

They would also quickly deduce that the envelope would be in the Glass Onion rather than in anyone else's rooms, because Miles is the kind of person who wouldn't have it any other way. Not sure whether Sally or Helen would get it first but the note is taken in half the time it is in the movie. It's already in their possession by the time the dinner happens.

They would solve the murder mystery bit really fast too, the only difference being that they would note their surroundings and solve it immediately after Miles gets "shot". At least one of them would clock the fact that Duke died of anaphylactic shock rather than a more traditional poison, possibly even as he was dying.

When everything comes together Grimoire and Sally both are livid. Grim has a perpetual snarl to his voice as he puts together everything in front of everyone cause fuck his usual way of doing things, he wants Miles to know that he knows and he wants that motherfucker to squirm. Sally is ice cold and practically spitting daggers at everyone in the room save for Helen, trying to get them to feel at least something for someone other than themselves. They'd both be trembling with rage whenever everyone else starts covering for Miles.

I'm not sure if Miles would burn the napkin or if Grimoire and Sally would be able to prevent that somehow. Either way, Helen would still break everything and burn the building down. Unlike Blanc who leaves before the explosion happens, Grimoire and Sally would stay because 1) they were transfixed by Helen's vengeance and 2) their near-death quota needs to be filled at some point. Lowkey I feel like both of them would live vicariously through Helen a little during the entirety of the final sequence.

Afterward

Someone I proposed this idea to was like "Makes sense that Blanc would crack Tangle Tower faster" but was stumped at the idea that Grimoire and Sally would be functionally similar in Glass Onion so I wanted to kinda show my thought process, if that makes any sense?

I'm not saying Blanc would solve Tangle Tower quicker because he's smarter than Grimoire and Sally, but because he's more in his element when there's an incredibly convoluted mystery for him to unravel.

He's not bad with people, per se, but does struggle with simply stupid individuals, always wanting to give the suspects and even the culprits the benefit of the doubt regarding their intelligence even when they're simply just Stupid. It takes him until the finale to truly realize and accept that Miles doesn't have an original, intelligent bone in his body, constantly in the belief that he wouldn't be that stupid, would he?

Yes. He would.

The suspects of Tangle Tower wrap up themselves in an ungodly amount of thread and Penny is pretty much hypercompetent, putting Benoit Blanc right in his element.

Furthermore, Grimoire and Sally are more candid in their approach of suspects compared to Blanc and that gives them the advantage in Glass Onion as they're quicker to clock certain parts of certain suspects, even when it's stupidly simple and not the result of a super satisfying mystery they've spent ages unraveling.

Look me in the eye and tell me that Sally, AKA miss "I saw the beetles in the laboratory and immediately knew that Pointer was just a stupid, materialistic asshole trying to get rich", would fall for Miles' shtick in any capacity. Look me in the eye and tell me Grimoire, contender for world's pettiest detective who scrutinizes the actions of all his suspects, would genuinely unironically be oblivious enough to not realize that he's dealing with Actual Idiots until the very end. Look me in the eye and tell me either of them would give the Disruptors the benefit of the doubt that Blanc gives them.