The LiFe batteries are an excellent choice to power your electronics without the need for a voltage regulator (UBEC). LiPo on the other hand need a voltage regulator to create an acceptable voltage of e.g. 6V suitable for the receiver and servos.

See topic Power distribution in your model  for more information about the possibilities and pictures of the different power distribution options. You will see pictures of possible configurations including batteries, switches, voltage regulators and power distribution systems.