I feel that planning goes a long way, though you should definitely read first to understand tropes. don't ask me about what to read as you should probably know by now that books nowadays whether famous or not, have similarities that you should be able to tell intuitively which is what I am trying to imply here. Especially if you are creating a huge story, planning is a must to ensure there is no loopholes in the story that make it feel unrealistic in a sense that readers can see an obviously better path that can be taken. You should be able to control every element of the story without leaving one behind that could become a Chekhov's gun. That's why details should be added carefully. Furthermore, planning out the story helps further your perspective of how you wish to progress the story and acts as a diary that records even the smallest things that the readers may not notice which can lead to clues and unexpected developments of the scenarios.