Sorry, what I meant by "not managed" was they just support PostgreSQL as in "yet another executable running on their containers", so they don't actually optimise or configure PostgreSQL for you.
I find Eloquent's approach to disconnect models from migrations a bit dangerous, but it could be me as I don't have much experience with Laravel. PlanetScale/Vitess doesn't support foreign keys, which is nice for distributed (planet scale, ha!) apps, but could be a problem for certain types of applications. I'd rather stick with (stock-ish) PostgreSQL.
Could do other things like directus (handles the api gen), planetscale has free mysql tier or even using airtable as the db, it provides the api part.