There's a WIP PR for silverstripe-elemental that adds the ability to identify which block is which on the preview pane.
Don't think there's one to do live editing on the page (that I know of)
Not yet, I had an idea for this for my old code I built in SS3, that i'm slowly making into react.
Exposing the InputField and the FieldHolder would allow developers to easily create their own custom field types that could not be done with a higher order component. An example of this would be a ...Hide attachment content
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