Q1) It is NOT possible to set the MaxPower value to each connected "device".
Instead, each device will have its own MaxPower value which will be indicated to the host through its descriptors.
Q2-1) The default value is indicated as 100mA which is intended for Self-Powered Hub.
For Bus-Powered Hub, it needs to be set as 500mA (FAh) to accommodate 100mA for each downstream device (4 x 100mA) + Hub power consumption (100mA).
Q2-2) It is recommended to set MaxPower value to 500mA if the application requires switching between Bus-Powered and Self-Powered modes.
It is possible to change the MaxPower value with the help of external EEPROM through Blaster Utility. To use Blaster utility, Hub needs to be bound to Vendor driver.