Regular flour aka all-purpose flour aka unbleached white flour is higher in gluten (protein) than pastry and cake flour respectively.

All-purpose flour has more gluten so it can bind more for things like yeast leavened bread. This extra gluten can make things a little too rough with things like cakes and pastries, hence, the need for a lighter flour.

All-purpose flour has a protein content of around 11% whereas cake flour has about 6-8%.

In vegan baking I would stay away from cake and pastry flours unless you're confident in your binding ingredient. if you're not using a binding ingredient you'll need the gluten in the all-purpose flour. BTW, soft wheat is what comprises most cake and pastry flours and all-purpose flour is more of a mix between hard and soft wheat.

Happy baking!