What is the meaning of preview parameters for poseEstimation CoreML

[adizhol]

❓Question

In Apple's doc for CoreML, there are two parameters for poseEstimation type of preview.
https://apple.github.io/coremltools/docs-guides/source/xcode-model-preview-types.html

What do they mean for a custom model I build?
width_multiplier?
output_stride?

Can you please provide a decent documentation for people?