Using 14 ga on part of a 20A circuit?
You can't do this unless you change the breaker to 15A. The 16 AWG wire as part of the lamps is allowed because the lamps, by design, will never have more power going through them. But the wires you put in could, someday, have additional power - perhaps another owner decides to put more lights or convert one to a receptacle for outdoor power tools. You can't control all of that (as much as you think you can) so you have to stick to the rules. 12 AWG for 20 A. 14 AWG for 15 A. You can have a mix of 12 &amp; 14 on a 15 A circuit, but can't do that on a 20 A circuit because the circuit breaker has to be small enough to protect all the wires connected to it.