Do i need capacitors

Yes i ve monitored the voltage, never less than 4.95V.. So you suggest me add capacitors to the servo motor and the DC motors?
I power arduino through the barrel jack, does it need a capacitor before that ? Is it a good idea to add a capacitor to the Bluetooth module ? Thanks again !!

Also, because the DC motors are mounted, and i don't really want to take everything apart, can i do something like the photo attached ? place the capacitors right to the motor driver's output A and B..