Well, it’s different. I only dabble in each of them.
Complexity theory has a number of names depending where it is found.
Systems theory is probably the most approachable. Its use in business goes back to the 1950s and much of it should be already familiar to you just as part of culture.
But one can go further back in time to Ecology. That gets complicated.
But if you know computing, computational complexity might be easiest. And of course there’s economics which uses whatever tricks it can find from any field to try to gain an advantage at explaining and predicting financial behavior.
Regardless of what you work with though, they all are compatible in some way.
I think the hardest thing you may find is: Time.
Time interleaves in complexity theory at various scales and I don’t know if the classes exist for equivalence.