Salt adds flavor. Fat tenderizes and emulsifiers contribute to fine grain and texture. Plastic fat with emulsifiers shortens more than liquid fat. Do not substitute oil for solid fat in recipes. Use specially formulated recipes for oil.
Sugar contributes to tenderness, fine texture, moistness, crust browning, and flavor.
Salt adds flavor. They may also be drier with a more open texture and have a more rounded top. The flavor may be less sweet, the cakes may dry out faster, and they will have less volume. Cakes with less fat may affect flavor slightly. It is essential in the correct proportion for jelling.