Concelaed LV wiring must be an 'approved method' and NM would fall into this group.

It can also get expensive very quickly since LV lighting uses much higher currents than 120 V lighting, and is very sensitive to voltage drop (dropping a few volts on 120 V does not have nearly the same affect on light output and color as dropping on a 12 V system).

It can become a real task to both handle the large conductors and than connect reliably and safely to the individual light conductors.

I would encourage you to check out individual smaller supplies that accept 120 V inputs and support 60 W of 12 V load per supply.
They are small enough to be mounted on the bottom of cabinets and then the rules for wiring are easier since nothing is concealed in the structure.

what about thermostat wire? i was looking into the heaters at school and they have 16awg for the tstat.

"what about thermostat wire? i was looking into the heaters at school and they have 16awg for the tstat."

LV lighting does not usually meet the V-A restrictions to use thermostat wire, the currents are WAY higher.

A single 20W bulb on a 12 V system is 1.7 amps.

he did say led, didnt he?

"he did say led, didnt he?"

LED is not low current either, especially with "the transformer will be located in the basement" running multiple banks of lights.