I spent way too long looking for good Ochako/Shouto fics last month, and honestly, the ratings aren’t super reliable across platforms. AO3’s kudos system gives you a decent pulse check—sort by kudos and filter out crossovers unless you’re into those. The pairing’s tag usually has a couple thousand fics, but a lot are just cameos in Deku-centric stuff.
What worked better was looking at authors who write for both ‘My Hero Academia’ and other Shonen series; they tend to handle the dynamic with more nuance, especially the whole ‘quirk marriage’ speculation angle. There’s this one longfic, ‘Thermal Equilibrium,’ that actually explores their families’ backgrounds instead of just fluff, which is rare. I’d start on AO3, then maybe lurk in the Ochako or Todoroki-centric channels on the MHA Discord—people share links there that never get huge traction but are seriously well-written.