I built products at Stripe as an engineer and never worked with an explicit QA team

I built products at Stripe as an engineer and never worked with an explicit QA team. Each team was responsible for the quality to a large extent. That being said, QA is definitely an important aspect of software development - regardless of who owns this work. Imo, instead of having a QA engineer per team or a few teams, you should have a QA shape role (similar to AVE you mentioned) that oversees a large area like an Org and pushes hard to make sure quality standards are held high across teams. It's also trivial for engineers these days to have great e2e automated test coverage with AI. We're actually building getlark.ai that helps engineers with this.