Switches for current source
My question is, which are the best components to use in SW1 and SW2?
  BJT or MOSFETS?


Use logic level mosfets with a low rdson, make sure you select mosfets that have a gate drive voltage (that works with 3.3V). If you use BJT's, you'll have rougly a 0.7V drop from the BJT which would be like using diodes and contribute to loss. 

Make sure mosfets are fully off or fully on (the gate voltage is either 0V or 3.3V) otherwise the mosfet could dissipate power.