Hello Mark,
1. A Service App requires two types of users: the developer and the full admin. You can read a detailed information about the workflow of Developer here - Service App Creation: Developer Flow and workflow of Admin here: Service App Creation: Admin Flow.
2. You should be able to transfer the app to another user within same organization, cross-org transfer is not supported. It is important to note that the person must have an active Webex account to take ownership of the app. Also, as per the Service Apps documentation:
For standard Integrations, if the authorizing user leaves the company or changes passwords, the Integration may break. In addition, unlike standard Integrations, Service Apps usually request data for many users and the whole org rather than on behalf of a single user.
Hope this answers your questions!
Best regards,
Rudrakshi Srivastava