58.4mA 459.7mW	53.2mA 418.3mW

Could a different buck converter save power? The DROK Analog USB uses 40mW more than the lower board of the DROK Buck Converter 5V-30V to 0.8-29V.

Turning the PWM off when it is not needed saves 3mW:

PWM on: 418.3mW	PWM off: 415.3mW

Finally, from https://youtu.be/urLSDi7SD8M

Letting unused digital IO pins on the Arduino not float (set as output, input, or use pullup resistors) can save 4mA!

Some floating pins	No floating pins
54 mA 414.2 mW	50.8 mA 389.7 mW