Whether there are appropriate registers to configure the FX3 to work only in USB2.0 mode? What is the power consumption of FX3 operating in USB2.0 and USB3.0 modes respectively
Yes. FX3 can be made to work only in 2.0 Please refer to CyU3PConnectState() API. If the second parameter is false, then USB3 Phy is Off and USB2 is On.
You can refer to FX3 SDK examples and the API Guide.
Please install FX3 SDK for the above.