@Esteban
if I max out at 6.8 * 24 = +/-160W and 1.7 * 24 = +/-40W, could that explain why there's no voltage drop?
Sure, but I doubt the measured values. Both @achrn and @dc42 have pointed out how to improve accuracy, but in the end, the Duet has to apply PWM to fine-tune the temperature of a heater, which might be the reason why your PSU can handle the load.
As soon as heaters arrive in PWM mode to regulate the current, they draw less power - on average. Cheap PSUs might be unable to deal with the spikes (that’s why ”Chinese Watts“ tend to deliver less ”bang” than you’d expect), but thanks to beefy capacitors and maybe some over-engineering, you are on the lucky side:
everything has always gone smoothly.
According to my static calculation (addition of nominal power requirements of all components), you are a bit over the limits, but as long as the voltage remains stable, there’s no reason to worry.