That format parameter in the Normal node should not be used anymore. Just let it generate the "default" normals, which should render correctly in the preview. Correct normals are then generated when exporting for each engine.
And yes, the tangents on the preview are wrong (was an issue in Godot's default meshes when I started Material Maker, and fixed since then).
You can indeed trivially modify the normals format as needed using Decompose and Combine, but I'd recommend SwapChannels that is easier. And if you need new export options, please ask. :)