Scenario answers
SCP denial
An SCP does not grant access. Effective permission requires an IAM or resource-policy allow and no applicable explicit deny.
Cross-account StackSets
Use organization integration where appropriate, target OUs, configure concurrency and failure tolerance, and validate on a small scope first.
Config remediation
Use scoped Systems Manager Automation with retry, rate control, evidence, and a documented exception process.
App configuration
Use AppConfig for validated progressive configuration deployment, not for arbitrary secret storage.