Which solution will meet these requirements?

Explanations:

Creating a new AWS account and sharing VPC subnets using AWS Resource Access Manager would complicate the architecture and introduce additional management overhead. This solution does not provide the necessary private communication channels between the microservices and would still rely on public internet access for inter-service communication.

This solution uses Network Load Balancers (NLB) in each microservice VPC and AWS PrivateLink to establish VPC endpoints, allowing for private connectivity between the services. Each service team can continue using their existing VPCs while facilitating secure HTTPS communication without traversing the public internet, thus meeting the security guidelines efficiently.

Creating VPC peering connections would require managing multiple peering arrangements, leading to a complex mesh of connections. Each service team would have to update route tables and manage the scalability and maintenance of these connections, making this solution less efficient and more error-prone compared to AWS PrivateLink.

While using a transit gateway allows for easier management of inter-VPC communication, it introduces the need for a new AWS account and additional complexity by requiring transit gateway attachments and route table updates. This solution would not minimize changes for each service team and could be overkill compared to using AWS PrivateLink for simpler and more direct communication.