Is generating a support ticket needed for closing an EC2 VPC instance?

You don't need to generate a support ticket before stopping or terminating an EC2 instance. You can perform these actions directly through the AWS Management Console.

There is an important difference between stopping and terminating an instance:

1. Stopping an instance: When you stop an instance, it enters a "stopped" state. The instance is shut down, but the EBS volumes remain attached and preserve their data. You will continue to be charged for any attached EBS volumes, but not for the instance hours. This is useful when you want to temporarily halt the instance but plan to use it again later.

2. Terminating an instance: When you terminate an instance, it's completely removed. The instance enters a "shutting-down" state before finally reaching "terminated" status. Any EBS volumes marked for deletion on termination will be deleted (losing their data), and you will no longer be charged for the instance or those volumes. Terminated instances will continue to appear in your instance list for some time before AWS reclaims them, but you are not charged for instances in a terminated state.

If you stop (but don't terminate) your instance, you'll only be charged for:

• The attached EBS volumes
• Any allocated public IPv4 addresses
• Any other persistent resources associated with the instance

If you don't need the instance anymore and want to avoid all charges related to it, termination is the better option. Before terminating, make sure to back up any important data from the instance's EBS volumes if needed.
Sources
How to make sure instances on my account terminate to prevent future charges | AWS re:Post
Managing Amazon EC2 Instances - AWS Toolkit for Visual Studio