There is a matter I'm confused about: What exactly is base-level reality, does it necessarily exist, and is it ontologically different from other constructs?

First off, I had gotten the impression that there was a base-level reality, and that in some sense it's ontologically different from the sorts of abstractions we use in our models. I thought that, it some sense, the subatomic particles "actually" existed, whereas our abstractions, like chairs, were "just" abstractions. I'm not actually sure how I got this impression, but I had the sense that other people thought this way, too.

And indeed, you could adopt an epistemology that would imply this. But I'm not sure what the benefit of doing so would be. Suppose people discovered lower-level particles that composed quantum particles, and modeling using these lower-level particles would provide high predictive accuracy than using mere quantum physics. But then suppose people discover sub-sub-quantum particles and that modeling the world in terms of these sub-sub-particles further yielded a more accurate world model than just modeling with sub-quantum particles. And what if this process continued forever: people just kept finding lower-level particles that composed higher-level particles and had higher predictive accuracy.

In the above situation, what's supposed to be taken to be base-level reality? Now, if you wanted, you could imagine that the world actually does have a base-level reality in the form of an infinite-memory computer, and that this computer dynamically generates new abstractions to uses them to compute what the agents see, making sure that it manages to start simulating things at a lower level of abstraction before any agent could reach the current "base-level" reality.

But that doesn't seem like a very natural hypothesis. If you keep finding more and more decompositions forever, it really seems to me that "there's no base-level reality" would be a simpler and more natural hypothesis.