The "S" in unreal is a tick. It's been about a decade since I last worked with Unreal but there was very much the concept of systems that processed batches of things in areas where performance was a concern.
Keep in mind that ECS is a design pattern and just like any design pattern applied blindly you can end up in a worse place than you started. A FactoryDispatcherQueuePatternImpl helps no one despite using many design patterns. When it comes to ECS it's much more about the spirit than the letter of the law.
Not so. The physics system works on all physics components. The renderer system works on all rendering components. The networking system work on all components that are enabled for network replication.
