Math alert:
My spiral trees have 42 pixels. That means 42 x3 =126 LEDs per tree.
2 trees are connect each controller. That means controllers have 252 leds.
So if we allow 20mA per LED.  That comes to a total of
252 x 0.02 = 5.04A.
* controller fuses have to be 5 Amps.

The spiral trees operate at 5v. To save on voltage drop I will run 12v to a small 10A dc dc converter that is located close to the controllers. 2 controllers will be connected to a single dc dc converter. That means it will supply 10.08Amps
10.08×5/12= 4.2Amps at 12v. (Assuming perfect conversion)
Realistically there will be about 20 to 25% loss.
4.2 / 0.8= 5.25 Amps or 4.2/0.75=5.6 Amps.
* dc dc converter
fuses have to be 5 Amps.