Honestly, you're hitting a sweet spot in Arcane fic that's exploded but still feels like digging for good stuff sometimes. A lot of the big ones go super heavy on the childhood friends angst, which is great, but I keep looking for ones that engage with the post-canon setting, you know? Like, what does that relationship even look like after the bridge scene? It's a minefield of character interpretation.
My absolute top rec right now is 'the ghost in the machine' over on AO3. It's a slow-burn that actually deals with Jinx's instability and Ekko's leadership burdens in a way that feels true to the show's complexity. The author doesn't shy away from the violence and trauma, but the moments of connection feel earned, not saccharine. It's got this gritty, melancholic tone that reminds me of the show itself.
Beyond that, 'Chronobreak (But It's Not)' is a popular time-loop fix-it that's fun if you're into that trope, though it leans a bit more into wish-fulfillment. 'scatterbrain' is a shorter, more experimental piece from Jinx's POV that nails her chaotic voice. I'd avoid anything tagged 'fluff' without a heavy 'angst' tag alongside it—for these two, the conflict is the point. The best stories make you believe, for a second, that they could find a way through the wreckage, even if you know it's doomed.