A powered USB hub will be better if you intend using several devices at once as the PC socket will not be overloaded. All USB devices will draw from the connection whether they are mains supported themselves or not. So if you have the keyboard (unpowered) and external HDDs (powered) on a single hub, the keyboard Wi-Fi will draw all its power to function and the drives some power to function. This may cause problems in an unpowered hub.
USB2 is backward compatible with USB1 but I am uncertain if any effect of having them both connected at the same time would cause a speed reduction of the USB2 devices. Given they are separate I should think they would function at their `normal` respective speeds. However if operating through the same connection there could be a data flow `bottleneck`.