Which is better testing approach for Kubernetes?

1. Ephemeral Environment : For development workflows, PR testing, or specific feature validation, where isolation from the main environment is crucial, or when testing under varying conditions.

2. Native testing Environment ( On Cluster ) : For ongoing integration and end-to-end testing as part of a CI/CD pipeline, especially with applications that are tightly coupled with Kubernetes.

Which one of the both should i go with?

And what are tools which would help me accomplish this?

Also with native environment, if too many developers are working on the same, it might bring the env. down , is also a problem.