Soy protein powder has had most of the fat and carbs removed, and therefore it’s much higher in protein than soy beans that have been ground into a powder (i.e. soy flour). Soy beans have around 33% calories from protein, whereas soy isolate can have >90% calories from protein.
It’s better to make tofu and using it as a homemade soy protein, since it will actually be more proteic.
Blend soy with water, strain, boil with vinegar and the solids will be your home made soy protein