What is the interval is to which component heights snap in the editor and how does that work with the defaultHeight that I set?

The vertical snap is 21px. While you can set a default height, there’s not currently a way to set a minimum height. So if you drag the component to be smaller than the default, it respects the new size you dragged to. When you set a defaultHeight, it renders to the nearest snap point, so eg a default height of 100 ends up at 106 when first inserted into the builder.