I think my question is more a USB spec question, since I'm not even sure if the HUB has to indicate between these two modes. Going through the USB 2.0 spec, I don't see the mechanism. It should be there, since the host needs to know if the total power budget of all USB devices and USB devices don't change their respective descriptors between the 2x cases.
Your understanding is correct. As per the USB Spec, the hub powered mode should be specified in the Configuration Descriptor. However, HX3 doesnt support bus powered mode and since it is a fixed firmware part, the mode is fixed as self-powered in the descriptor.
Ok, thanks Sananya. We will use it as self-powered mode, so no problem for us.