If you populate the USB 2.0 ports with devices that draw about 500 mA current, then some of the devices may fail to operate properly. Although the current capacity of the USB 2.0 ports is rated 500 mA per port, unfortunately they do not work well at that rating. If you want to use high-current devices, then you should use a powered USB hub.
You can continue using direct from USB 2.0 ports on the motherboard devices that operate under 100 mA, such as mouse, keyboard, USB printer, webcam, USB flash disk, etc..
Current capacity for USB 3.0 port is 900 mA, if I remember correctly.