Hi,
Fetch this collection automatically means we will fetch the collection when a page using this collection is loading. So you don’t even have to add a fetch collection action in an on app/page load workflow. Feel free to uncheck it if you want to control yourself when you want to load this collection for the first time.
Preserve on navigation mean the collection will not be reset or refetch when navigating to another page.
You can limit the amount of records the query returns by configuring the Query configuration step (you don’t have any pagination yet but you can set it with 25 items for exemple, and you will receive only 25 items).