API Authentication

On-premises Orchestrator can use:
basic authentication
the OAuth flow (2021.4 and later)

Automation Cloud, and therefore Orchestrator as well, can use two mechanisms:
tokens instead of basic authentication. More...
the OAuth flow

Libraries Feeds

For on-premises Orchestrator, you can publish libraries both at host and tenant level feeds

In Automation Cloud you can publish libraries only at tenant level. To share libraries between tenants, you can use a custom feed.

Password Complexity Settings

As an administrator of an on-premises Orchestrator, you can manage the password complexity for your host or organization.

By default, when users sign up for Automation Cloud and create their account, the password they set must meet specific requirements, which cannot be modified.
You can choose to change your Authentication Settings to use the Azure Active Directory integration, which allows you to configure password requirements.