At the heart of it, there are four throughlines with unique problems. The OS is Objective and impersonal. The IC and MC are our subjective characters and have a bit of oil/water going on with the Objective stuff.
Does the IC have their own problem? That's a great question, and there are two ways to go about learning this:
1. The IC has their own problem: this is how I learned it, but...
2. The IC is the you perspective in a story, meaning that I am looking at you. That's a better way to look at it. Think always about the effect the IC is having on the MC. They are an obstacle, an impediment, a hiccup in the way the MC wants to go about doing things.
So, while a very optimistic IC can be looked at as "Hey, that IC is really boppy" and it'll work, it's a smarter plan to look at the IC and ask, "Is this boppy nature of the IC affecting my MC?"
You can look at my answers in this thread to see an example of how and IC can affect an MC.