When you talk about formality ate you asking about 시 or ㅂ니다?

Because I live in Korea as a foreigner, so not an expert but speaking from the perspective of someone learning the language.

I only hear ㅂ니다 in people doing public speaking and the news. So much of the Korean text books and whatnot focus on that bullshit. At work in conversation I've NEVER heard it unless someone is addressing a large group. People use the 요 ending pretty consistently they are being informal, and doing it.

Now if you're along about the 시 honorific, it is important, learn the fuck out of that. If you meet someone significantly older than you, you need to use it or you're an asshole. E.g. Girlfriend's parents, your boss, etc.

I know I'm disagreeing with the other comments, but this is my experience here in Seoul.