Why should I bake baking soda for making ramen noodles?
Baking turns bicarbonate of soda into a weak form of lye - sodium carbonate, as you said. It basically makes it a stronger alkali. The actual baking process is safe, but the resulting lye is an irritant and you should avoid getting in on your skin, and definitely avoid it getting it in your eyes.

The difference in texture and colour is noticeable after baking. The texture will be finer, and it will be whiter.