When downloading various usdz files for use with RealityKit, how do I know which child to use?

Question

Want to preface that I'm a SwiftUI dev & complete newbie to working with Vision/ARKit

I'm starting to get into VisionKit and I'm playing around with RealityView and placing entities. From my understanding .usdz files are the go to for getting 3d renderings here. From experimenting with a few various files, It seems usdz each has their own file structure.

Sometimes using the wrong child results in the model being completely blown up. Other times when I add physics and gestures it causes them to not work. I was wondering if there was a proper way to determine which child to use, and also if anyone has an explanation it would be super helpful for my understanding.

RealityView { content in
    if let model = try? await Entity(named: "SampleModel").children.first?.children.first {
        content.add(model)
    }
}

Thanks!