One thing I forgot in my previous write-up on set-pieces: set-pieces are relatively modular. By this, I mean that you can swap them out and replace them without changing much else in the story.
For example, I mentioned the meet cute as a common set-piece in movies. All that’s necessary for a meet cute is that the two leads meet in some entertaining way. Also, at the end of the scene they usually have to have developed a certain attitude toward each other (often initially hostile).
For a good meet cute, your couple might meet at work, or in a gym, or at the dentist’s, or in a fender-bender. It doesn’t matter. All that the plot requires is that they meet and establish that starting attitude.
So let’s say your original plan is that the two will meet when their dogs get into a fight at the dog-park. But once you start actually writing the story, you might get a better idea. As you develop the characters into more rounded people, maybe you decide that one of the romantic leads likes to do science fiction cosplay…so maybe the meet cute will happen when that person is dressed as a Klingon. The Klingon locks their keys in the car, and is trying to break in when the other person (a cop) shows up.
So you try writing that scene. If the result isn’t as good as you want, then you can try something else. Plotwise, it doesn’t matter as long as the two meet.
You can replace a set-piece with something very different, if ever you come up with something that will serve the story better…especially if you think of something that better reflects other parts of the story (e.g. character traits that you discover as you write). Eventually, you’ll have to smooth everything out into a well-connected whole, but that’s what revision is for. When you’re just starting to write a story, your set-pieces are provisional and replaceable. You want them to be good, but you shouldn’t consider them cast in stone.