Unlock the Secret to Perfect Storytelling: How Many Viewpoint Characters Should Your Novel Really Have?
If you have a largish number of viewpoint characters (5 or more), then some of them are not going to get many scenes. At least one of them will get no more than 20% of the scenes.
And if you have a LOT of viewpoint characters (15 or more), then some of them might be walk-on characters who only star in one scene. That’s okay. That can work. If you need that many to make the novel work, then do it.
My opinion is that the number of viewpoint characters you choose is probably not going to mess up your novel. What makes or breaks your novel is the quality of the viewpoint characters—how well each scene works. If you make sure that every scene has a really solid viewpoint character, and if your main story has a solid protagonist, then the count of viewpoint characters is not a major issue.
