1. that the 7805 can be used as is to drop the 12v to 5v,
2. that one should add 2 capacitors to the step-down circuit.
Quote1. that the 7805 can be used as is to drop the 12v to 5v,Wrong
There is no difference in safety, 12V and 5V are equally safe. Remember a child's train set has 12V exposed rails.Local regulation however is better to minimise line volts drops.
Pesonally, I would connect the LEDs in string of 4 or 5 with a current limit resistor and run them from 12V if that is an option.