I’m glad you found Heron on the Package Manager. Now that Heron v0.4.0 has been released, I plan to update food4rhino with an example file when it’s ready so there will be less confusion.
When using Heron, typically the first thing to do is set the Earth Anchor Point close to that of the data with the SetEAP component. Fewer errors will arise when this is done.
This will make sure all the data is coming in close to Rhino’s origin. Both geojson files you posted work when this is done. Note, I’ve unchecked “Clip with boundary” from the menu so that no boundary curve is needed.
I’m not sure I understand your last question, but overall I think geojson is a great GIS filetype. If you get the data in a projected coordinate system (ie EPSG:5179) you will probably have more success with the various plugins.