Owner vs Organization Adminstrator vs Billing Account Adminstrator

Unfortunately there isn't a "super user" role that will allow you to do all the things in GCP.

Owner is indirectly the super user role because with Owner role you can give yourself all the other permissions/roles that you need.

You can create a custom role (say superuser) and add all GCP permissions into the role and assign it yourself, but this becomes a mundane task. This comes with a limitation of 64 KB max role size and is left for experimentation.

Note: Organization level and project level roles are different, and owner of a project doesn't mean owner of an organization.