No capitals needed. I have written many backend services around raw Vertx very successfully. It's simple, well documented and predictable, mainly because everything is done in code.

Deviating from Quarkus's standard behaviour was comparatively difficult, either tracking down the correct configuration properties and what to change them to, or which api to implement and override and what it needs to do.

I prefer to develop OpenAPI specs separately from the code too, mainly because it's a joint effort with other teams. Vertx can incorporate them easily.

If you're generating the vertx route handlers from the spec then I guess that's fine.