Well but this plus/minus/ground example would not apply to USB devices right? i mean USB is USB. it always fits.
But i will be more carefull next time for sure! 
Anyway, hope the Vive adaptor works with Pimax, or that the Pimax adapter will work with the old Vive. would be ideal! not going to buy both wireless versions.
Voltage isn’t how much power is being drawn. Everything you plug into your 220 volt mains power is 220 volt, but they each draw different amounts of power.
Your usb ventilator does require 5 volts - that’s what it’s designed for. That doesn’t say how much power it draws.
Your 220 volt pc uses a 220 volt connection from the power point to the power supply (the very first thing the cord goes to) but from there is no longer 220v but all different voltages including the 5 volts that runs to your usb which supplies your ventilator.
You need to only plug in 5v things into that charger. They can then draw up to 2.1 amps, but less too. Most things using usb plugs are 5v 1 amp or 5 volt 2 amps draw and thus that charger will cover most things.
Thanks for explaining 