Manolo/Joaquin fic often lives or dies on the hidden injury trope. Manolo's the golden boy with a smile for everyone, but he's got layers of Catholic guilt and family expectations wrapped around him tighter than bull-leather, and nobody seems to notice. The conflict writes itself when you flip it: Joaquin, the decorated soldier, has visible scars everyone fawns over, but it's Manolo's invisible ones that finally make Joaquin snap. He gets tired of being the 'stable' one while watching Manolo quietly drown in duty. I've seen a few where the real conflict isn't about the romance itself, but about Joaquin trying to pull Manolo out of that sacrificial-martyr headspace before it consumes him. The best ones have them both wrong about what the other needs.
And then there's the classic 'San Angel thinks they know them' angle. Manolo's the town's beloved musician, Joaquin its brave defender—they're public property. Any tension between them becomes a public spectacle, gossip fodder for the plaza. That external pressure cooker forces them to either double down on the lie or finally blow up. I read one where Maria, of all people, was the one shielding them, running interference because she knew exactly how smothering that adoration could feel. It added a nice layer beyond the usual love triangle stuff.