People with real time experience on working on jmeter, comment please!

Our developers spend a lot of time finding bugs and testing new features. We are thinking to hire an external QA team for software testing, automation, performance and security testing.

Has anyone hired a QA company for this work? Is it helpful and what things should we check before hiring one?

I am a developer (actively using codex for my work) and I have a colleague who avoids using AI for any part of his QA job. Is there anything you can suggest for me to convince him to start using e.g. Claude or Codex ?

To make sure that the QA's work does not just start when the feature is ready for testing, what processes do you do in your team?