I've always preferred creating short stories, and novels naturally. I don't normally create plot summaries, chapter summaries, and so forth. Is it best to always create a plot summary and chapter summary with at least key plot points before digging into actual writing?
It is best to do what works best for you (and you will have to try). People (and writers) are different, and what works for one need not work for another.
If you find that what you write without plan is reasonably well structured and without disabling plot holes that make rewriting and cleaning up a nightmare there is no reason why you should insert an unnecessary additional step into your process just to satisfy the authors of how to write books.
If on the other hand you find that the result of you happily writing along falls below your expectations you might profit from however much planning helps you avoid whatever went wrong. You'll need to analyse your works, maybe get feedback from readers, and then find appropriate strategies. These might include defining the end, setting up certain key events, writing a premise or logline, drawing charts, or whatever. I once wrote a novel guided by a series of photographs as landmarks. There is no generally applicable advice, and you'll have to experiment to find your own ideal procedure.
An outline or summary is planning. As is character profiles, event lists, setting notes, language notes, maps, roleplaying, and anything else you do understand the story before you write it. How much planning is needed varies from none at all to months of planning for hours of writing. Some factors that affect how much planning is needed are length, complexity, abnormality, number of authors, memory and writing speed. The longer the story the more details to be confused, and the same with complicated plots esoteric theories and other complications. If you can't remember the whole story for long enough to write it down, you need notes. If you are working with someone else, you need to plan to make sure everyone has the same plan. Abnormality? The more different a story is from what you know, the more you need to plan.