1. dynamic losses would lower the output depending upon the load.
2. on/off delay losses would lower the output voltage independent of the load but dependent on the ratio of switching time period to on/off delay of switches.
3. the derivation of these formulas are very basic in nature and can be found in any power electronic book.
4. Since the formulas are not in the frequency domain, it will be incorrect to call them "transfer functions". They are simply the Gain and not Transfer function