https://www.mobilenewscwp.co.uk/2018/10/15/oneplus-strikes-ranging-deals-with-carphone-ee-and-vodafone/ One Plus 6T when it arrives will be sold elsewhere other than O2 now which is great news
I have the red one and purchased direct from OnePlus. Very happy with the handset and the quality is immense. Cannot fault the speed and power of the OS and with the recent upgrade to Android Pie it's still running great.
The a6000 model is the Chinese model. A6003 is the global version. This does have band 20 apparently, but I think it means someone as flashed the Chinese os off and put the oxygen os on. I always get nervous when hearing this.
It is a usb 3.1 cable, unless you mean transfer speeds, and it seems very fast. The Poco thing does not have Android 9 yet, and it not guaranteed to get 10. Also the camera does not support 4k 60fps according to gsmarena. So there are chunks in its armour. Also the notch is iPhone noob size.
Ffs give it a rest mate