Please consider that I'm new to AWS administration.
I have full access to my organisation's AWS account. One of our website(developed in Drupal) is developed by a vendor who hosts it in their AWS account(dev/prod env.). They have a master account and separate accounts for each clients.
My organisation wants to migrate the entire infrastructure in-house in our own AWS environment, which does seem to be a great idea. Meanwhile, I've found AWS Organisations and I know I can invite vendor to join our organisation and then we can restrict their access(only development access) and mange the website and respective infrastructure ourselves. But this means we will have the control of their root account, which won't happen as they have other client accounts as well.
In this scenario, please suggest the best way to get full access and control to only our account?