My advice will be a bit counter intuitive. I wrote a 90 page story that was well planned out and all I used were bullet points for each chapter. Beyond the current chapter I had no idea where I was going, but I made it work regardless.
I think an important factor for writing a well realized/planned story is the scope. If the scope of the story is beyond your imagination or capability then of course it won't turn out well. Before writing my 90 page story, I wrote a 40 page story. I didn't work nearly as perfectly as my 90 page story, but it still worked. My point is that it's best to start small and work your way up.
Why do people plan things out? Because it saves time. When I was writing my 40 page story I didn't even use bullet points. But I was able to do the job regardless because of how short the chapters were, but when it came time to extend my chapters with my 90 page story I started wondering what would happen next in the middle of chapters, halting my moment completely. My point is you only need to plan as far as you need and as far as you need is defined by factors like how long the story is or how well you can recall what you were trying to do after writing so and so for a certain amount of time. So obviously if you're writing a 200 or longer story you may in fact need something more than bullet points.
Now let's define a well planned story. It requires a well realized plot that starts from chapter one. Now that sounds like a hard thing to do, or nearly impossible if you're only writing it chapter by chapter, but I was able to do it. I started my story by introducing the world and characters, but that wasn't the real, real start of my story. The story actually started when I introduced the main characters goal and the story ended when he achieved it. Now that may sound boring at first glance but it's not about what my character literally does, it's about what it represents. My MC wanted to get better loot in a video game. The journey was all the things the MC had to go through to get it. All the choices that had to be made. My MC was fairly clever but he was unable to obtain what he wanted without the help of others. It's not a very original theme, but none really are. To have a well realized story, you need to have a theme or character arc/s. But you can't do it to the point that it's obvious or unnatural or shoved in for no reason. You have to write the story by itself without having a specific theme in mind prior to writing. Like have it in the back of your mind but don't let it be the main focus.
Edit: I accidentally posted this while trying copy/paste a part of it before I could finish my point, so I'm just going to leave it as is.
