The parameter store was not available at the time Strongbox was designed and developed. The Strongbox project page has a nice matrix comparing how Strongbox stacks up against Parameter Store.
In terms of not using credentials directly, relying on AWS KMS for encryption keys, and the use of IAM policies to control access to secrets, Strongbox and AWS Parameter Store share a similar design.
In terms of not using credentials directly, relying on AWS KMS for encryption keys, and the use of IAM policies to control access to secrets, Strongbox and AWS Parameter Store share a similar design.