Specify exact parent child relationship between two blocks

Question

I’m not sure about the second one (removing the wrappers), but as for limiting the allowed blocks:

First I want to make it so that the ONLY block that can be added as a
child block of the feature-cards is the child block. How can I
enforce this?

You can use the allowedBlocks property of InnerBlocks like so:

// In the edit() function of the feature-cards block type:
el( InnerBlocks, { allowedBlocks: [ 'feature-card' ] } )

And you should know that wp.editor.RichText is deprecated, so use wp.blockEditor.RichText instead. So in your feature-card block type, you’d use var RichText = blockEditor.RichText; and not var RichText = editor.RichText;.

Also, you might also want to use useBlockProps in your code. 🙂