Thanks but what about power? To connect to a recent lap without built-in NIC, also when external HDD plugged in on another USB port
I'll be assuming that you have a usb3.0 to gigabit ethernet adapter The power usage of those adapters is really low so that shouldn't be an issue. If your computer only has usb2.0, the max throughput will be 480mbps. So, even if you use a gigabit switch/router and the operating system says that it's running at 1gbps you won't have its full speed. If you connect using usb3.0, the speed won't be limited by the interface. So you will have the full gigabit speed with a little more latency because of the usb protocol overhead. Remember, each usb port is connected to an internal hub and it shares the bandwidth between the devices. The more usb devices that you have on your computer, the less speed available for each one.