AWS Redshift cluster nodes have to be of given type.
There are two different ways to resize your Redshift clusters; to find the method that fits your needs, see the AWS documentation.
In Terraform -
References:
https://docs.aws.amazon.com/redshift/latest/mgmt/managing-cluster-operations.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/redshift_cluster