Its not clear what you intend to do with this.
Firstly, a 16A supply to a USB socket is asking for problems, including possibly fire risk from overloaded copnnectors and cables. The USB circuits are, I think, the internal connection in the Samsung and Apple devices although they may be different from one model to another. USB allows for the DC voltage from the potential dividers to be used to program the charging voltage and current limits in the power source but you can't connect more than one at a time in parallel.
The 16A supply is OK although probably not needed if you have 12V available already but I suspect what you need is 8 individual USB charge controllers so each can feed one load regardless of what device is plugged in to it.
Brian.