In this reference, you will find all resources that are defined in this API. Please note that depending on the provider, there are also provider-specific custom resources that are important to use this operator.
Have a look in the documentation of the respective provider integration to find more details of how the provider-specific custom resources look like and how they can be used.
The only user-facing CRD of the Cluster Stack Operator is the ClusterStack. Apart from that, there will be, depending on a provider, a ProviderClusterStackReleaseTemplate, which gives provider-specific information and has to be applied by the user.
To see all CRDs, including the ones that are not intended to be applied by users, see here.