Mac instances run macOS 10.14 (Mojave) and 10.15 (Catalina) and can be accessed via command line (SSH) or remote desktop (VNC). The AMIs (Amazon Machine Images) for EC2 Mac instances are EC2-optimized and include the AWS goodies that you would find on other AWS AMIs: An ENA driver, the AWS Command Line Interface (CLI), the CloudWatch Agent, CloudFormation Helper Scripts, support for AWS Systems Manager, and the ec2-user account.