In the movie the setting is very important because almost everything happens in this fancy apartment building called Whitehaven Mansions. It's where Poirot lives, and the murder happens just two floors below him. This setup makes the whole thing feel really close to home for Poirot, which adds to the tension. Plus, we get to see all these cool parts of the building like the elevator, stairs, and even a weird coal lift, which plays a big part in the story.
As for the point of view, we mostly see things through Poirot's eyes, but we also get to follow the group of young friends who accidentally stumble onto the murder. This mix of perspectives is pretty clever because it lets us see both Poirot doing his detective thing and the regular people freaking out about finding a body. It makes the story more interesting and lets us in on stuff that Poirot doesn't know right away. Also, seeing Poirot in his own building, dealing with a cold and all, makes him seem more human and relatable, which is kinda cool for a super-smart detective character.