AME Wizard is controlled by Playbooks, a heavily customizable script-esque system that can perform a wide range of tasks, including deep modifications to Windows. AME Wizard's backend is open source, meaning that you can see exactly what is ran.
Playbooks are renamed .zip archives (with the password malte) which primarily consists of plain text scripts, meaning that Playbook is much easier to audit to see exactly what is changed. This is unlike custom Windows ISOs, which have many more entry points for malicious activity.