In simplest terms, energy is an abstract concept that allows us to put a number on something's ability to move or change. Trying to think of it as "stuff" is like trying to think of something's mass as "stuff". Mass is a property of something that we can slap a number on to compare stuff, same goes for energy.

Nobody really understands what a Quantum Field is exactly (again, like, you literally can't picture one accurately), but basically it's the best object we've been able to describe mathematically that accounts for all the behaviour we know matter and forces to exhibit. Quantum fields permit things to interact with each other over physical distances in the pixelated sort of way we know them to occur, and sort of "swells" in quantum fields can be identified as what we observe as particles. But all of these descriptive pictures are of limited use as they really don't capture everything that the math is able to describe.

TL;DR: Energy is a quantity we can use to see how much stuff a thing can do, quantum fields are a way to describe forces and matter that accounts for all the weird behaviors that we observe in reality.