Stopping presence on AWS for a while. What backups to do so we can restore our presence later?

Hello.

With EC2 and RDS, by creating a snapshot etc. and then deleting the instance, you can use that data when you want to restore it later.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-creating-snapshot.html
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_CreateSnapshot.html

Also, outputting AWS resource configuration data to a CloudFormation template should be useful when you want to use AWS again.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/generate-IaC.html