The Get Streams endpoint will return data about a stream at the current point in time, if you wish to get data over time you’ll have to periodically poll that endpoint.
For chat activity, you’d need to connect to chat and track that sort of data yourself as it happens.
EventSub Can also provide a lot of data on various topics in near real-time.
No, the API does not provide historical data or summaries. You will need to collect and store that data yourself as it happens.
There is some historical data such as the existence of VoDs, or Clips, and their various details such as views, but that’s about it.