What does your choice of the viewpoint character have to do with plot? Actually a whole lot. Whether you choose to use a single character, two, three or more their eyes and voice will drive the plot. Let's look at some ways.
A single viewpoint can be in first, third and probably second person. If you choose a single person to tell the story the only things you can reveal to the reader are what this character sees, hears, feels and does. This can have limits and may make telling some types of stories difficult.
Choosing two or three is what many authors choose. Here they can use a hero, a heroine and a villain. Or just a hero and heroine. What this does is give two or more sides to the story. This works well in many genres. Here there are two or three voices and eyes to show what's happening. Confusion can come when the writer shifts the viewpoint character and manages to muddy the plot.
There are two types of multiple character viewpoints. One is omniscient where all points of view are given but the writer is actually the person telling the story. This can become confusing and the reader can get lost. Sometimes the writer manages to switch the viewpoint in the middle of a sentence, Not comfortable for the reader.
The second kind of multiple viewpoints is to have a group of characters each with their own chapter or scene and showing the action through their eyes. This can be difficult when the writer forgets whose head they're in.
Though some writers switch viewpoints during a scene others don't. Too frequent switches make the reader feel like they're watching a tennis match.
No matter what kind of viewpoint you choose to write remember you should establish the pattern early in the story and stick to the pattern. Changing midstream or at the end of a book can confuse the reader.
Remember while writing the story you can change your mind about what viewpoint to use. Sometimes experiment with shifts can make the plot come alive.