Musing about concepts like simulation complexity or energy requirement is essentially worthless if you don't know the rules on the outside.
For example, suppose that there's some root-universe (or much-more-root-than-apparent-universe, anyway) which simulates a child-universe, that simulations a child-child-universe, and so forth. If the rules of simulation and mechanics are distorted/reduced along the way, then it may be the case that higher-level universes would lack any logic to be parallel to a lower-level universe, making the lower-level universes fundamentally beyond conception.
(Example of "beyond conception": Imagine if a god appeared before you to truthfully explain a new type of physical particle/whatever that exists in the universe. However, the particle described operates according to a complexity so vast that making any predictions based on knowledge of its existence would be infeasible -- you'd need a computer larger than the observable universe to make even the most trivial of predictions in the simplest of cases. Then, even if you looked and tried to find examples of the particle, you couldn't, because you couldn't compute a prediction to align with the hypothesis that you're looking or not looking at one.)
And so, an analysis of apparent-complexity would seem insufficient to eliminate the concept of being a simulation within some more-root-universe.
That said, we can still consider notions of universes more ontologically local to the apparent-universe. And so it might be more interesting to consider not the question of IF the apparent-universe is being simulated, but rather what the space of productive notions of plausible outside-universes might be.
Also, if in the future we start simulating universes, all these constraints will apply to us and all the simulations we do.