Multiple USB power inputs in parallel
First, it's a BAD idea to connect multiple power sources in parallel without any protection at all. Imagine one of your power sources give 5.05V, the other one gives 5.00V. One power source will send current to another one, and these power sources are not designed to sink current. And since no power source is perfect, they will always have slightly different voltage. So just no to that.
A common practice is to put two schottky diodes that meet on the line you feed. You will drop about 0.15V, but usually it's an OK price for such an easy solution. Of course you could design some circuit that switches the sources and makes sure only one power source is attached to power line at a time, there's a dozen ways to do that, you could use back-to-back MOSFET to detach lines from the circuit, it's a common practice in laptops when you choose between powering system from battery or from charger. You can find double schottky diode there too, by the way.
Picture 1: double diodes
Picture 2: double mosfet back-to-back in macbook air 2011-2017. Air also has double diode in another place.