I wonder what would be the risk when a psu has for example 400W at one 12A line and i would power one board directly and 3 others with cables? I could use 3mm speaker cables if that helps...
You risk that the weakest part melts.
The power for the 3 others has to go through the PCB from the direct connection to the green terminal then.
burnin already recommended to only connect two boards and use
solid wires. I would just follow his recommendations.