If you substitute self rising/raising flour for plain or all purpose flour without removing the appropriate amount of baking powder, then your cake will be over-leavened. It runs the risk of collapsing.
Self rising/raising flour is a wheat flour with a protein [gluten] content of 9-11% that includes baking powder.
Plain or all purpose flour is a wheat flour with a protein [gluten] content of 9-11% that does not include baking powder.
Cake flour is a wheat flour with a protein [gluten] content of 6-8% that does not include baking powder.
Plain or all purpose flour recipes have baking powder or other leaveners* included in their ingredients list. *Leaveners, other than baking powder, include bicarbonate of soda [baking soda] plus acidic ingredient or yeast.
You may substitute self rising/raising flour for plain or all purpose flour plus baking powder if, and only if, the amounts are equal. That is: if the recipe lists 1 cup US plain or all purpose flour plus 1 1/2 teaspoon baking powder plus 1/4-1/2 teaspoon salt then you can use 1 cup US self rising.
Recipes that use self rising/raising flour do not have baking powder or leaveners in their ingredients list.
Their are numerous recipes available that use self rising/raising flour. Both Britain and Australia have a tradition of using self-raising flour.
Example: Butter cake
8 oz butter, softened
1 1/4 cup sugar
2 teaspoons vanilla essence
2 3/4 cups self-raising flour
2/3 cup milk
Preheat oven to 360°F. Grease and line 9" round cake pan with baking paper.
Using an electric mixer, cream butter, caster sugar and vanilla in a medium bowl on medium-high speed until light and fluffy.
Add eggs, 1 at a time, beating to combine. Add half the flour with a spoon. Stir to combine. Add half the milk. Stir to combine. Repeat with remaining flour and milk. Stirring with a spoon does not "toughen" the cake texture.
Spread mixture into prepared pan. Bake for 40-45 mins or until a skewer inserted into the centre comes out clean. Stand in pan for 10 minutes. Turn out onto a wire rack to cool. Dust with icing sugar. Serve.
Plain or self-raising flour? It does not matter as long as the recipe is appropriate ..