How is USB Bandwidth shared?

I'm looking here at the specs of two notebooks.
One has 3 USB ports but just 1 USB 3.0, the other 3 USB ports too, but 2 USB 3.0 ports.
The crux with the second is, that the 2 USB 3.0 ports are on the same controller.

So there is no difference in transfer speed between using the first with a usb3 hub connected and the second straight, when i want to transfer data between two external USB 3.0 drives, right?

I'm a bit iffy on the whole USB topic. Maybe someone can clarify a few other things too.
- Bandwidth is share between devices connected to the same Root-Hub or is it the same Host-Controller?
- USB 2.0 devices connected to a USB3 port, can still only share 480MB/s?
- does a USB 2.0 device, dig into the available bandwidth to a USB3.0 divice on the same USB 3.0 port on the computer or run USB2 and USB3 completely independant even on the same cable?

Thanks and