Real-time Statistics augment existing statistics. However, they are not quite as real-time as the name suggests. To keep their implementation lightweight they use the table monitoring mechanism, this limits the information that can be collected.
High-Frequency Automatic Optimizer Statistics Collection is effectively a never-ending statistics maintenance window. As your data and statistics change, so there are opportunities for SQL execution plans, and therefore application performance to change. DBAs and developers need to be aware of the implications.
The video of this presentation as a part of the Oracle Groundbreakers EMEA Tour 2020 is available on YouTube