You are the project owner of a GCP project and want to delegate control to...

Storage Admin (roles/storage.admin) Grants full control of buckets and objects.

When applied to an individual bucket, control applies only to the specified bucket and objects within the bucket.

firebase.projects.get

resourcemanager.projects.get

resourcemanager.projects.list

storage.buckets.*

storage.objects.*

https://cloud.google.com/storage/docs/access-control/iam-roles

This role grants full control of buckets and objects. When applied to an individual bucket, control applies only to the specified bucket and objects within the bucket.

Ref: https://cloud.google.com/iam/docs/understanding-roles#storage-roles