Formal and Informal speech

[Anomalocaris]

Is it formal to use everyday words and informal to use big intelligent words? When you use a big vocabulary is that too formal when talking to people? Like Tarantino, is he formal or informal, or both? He uses alot of big words in his movies, when you use big words is that too formal?

You just use language based on the audience. If your audience have to reach for a dictionary when you type then you are being too loquacious pretentious for them.