I use the standard button layouts with only 2 back paddles attached. 4 seem too much for me.
The left one is configured as the “Shift Button”. It replaces the function(Fire Button) of the Right Trigger with the Switching Weapon button (Y) once the Shift Button is pressed. Whenever I exhaust a clip of the Primary weapon I then quickly change the weapon by pressing the Right Trigger (the Left Paddle is pressed/Shift Function) and start shooting my secondary gun faster. This setup also provides a better overall character control (moving and aiming), since I don’t have to move my fingers from the sticks. The right paddle is configured as the Jump button (A) for the same reason to keep my fingers on the stick at all times.