How to debug ansible variable precedence

Question

I have a complex ansible setup which I want to refactor, with variables defined in various places / at various levels. I am aware of the basic inheritance rules: https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#ansible-variable-precedence

I would like to do a verbose debug run, that dumps all the variable key-value pairs to stdout or a file - as they would be effectively applied to my host or environments, but without actually applying any playbooks.

How can I do that with Ansible?

Also, how can I get Ansible to show which yaml files it sources in which order (e.g. what it has found where)