Hm, that's a pairing I don't see pop up too often in the main 'UnOrdinary' spaces. Makes it a fun little niche to dig into. I've always felt the best stories lean into the 'enemies-to-allies-with-a-common-goal' dynamic rather than a straight-up enemies-to-lovers. Their initial meeting was so hostile, so a good trope has them forced into a temporary alliance—maybe against a third party like the authorities or Ember. Watching them navigate that fragile trust, balancing Poppy's rule-following pragmatism against Looey's chaotic, results-driven methods, creates a ton of tension.
Found-family angles work well here too, but in a weirdly inverted way. They're both outsiders in their own respect, but Looey's crew is already his found family. The more compelling thread is Poppy, who's so institutionalized, being reluctantly folded into that messy, loyal group. She'd hate their lack of structure but secretly crave the belonging. A slow-burn where she starts covering for them or using her position to subtly aid them, all while denying any attachment, hits the spot.
I'm less sold on high-school AUs for them; it strips away the crucial power dynamics and high-stakes context that make their clashes meaningful. The best fics I've bookmarked usually keep them in canon, maybe post-Safe House, exploring the bureaucratic nightmare of Poppy trying to 'reform' Looey while he constantly undermines her with a smirk. That push-pull, the gradual erosion of her black-and-white worldview, is the real draw for me. Ends up feeling more like a character study than pure romance, which I prefer.
Honestly, the trope that falls flat is instant forgiveness. Any story that has Poppy just get over his attempted murder because he's cute needs a rewrite. The resentment has to linger, and the best authors let it simmer under the surface of every interaction, making the eventual truce feel earned.