Less sugar may result in less browning, less tender texture, greater tendency to tunnel, greater tendency to dry out, and a less sweet taste. Less fat may result in a less tender and dry texture and a greater tendency to tunnel. Reduced salt may affect flavor slightly. Keeping time will be shortened. Fat separates the flour or starch granules to prevent lumping during cooking.
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.