Can echo flex be used as a smart plug

Think of it more as a microphone extension to your existing Echo device - it doesn't have the ability to control itself - you would need another device to perform switching tasks...
As for the USB port - you can use it to connect devices for charging, or plug in one of Amazon’s accessories, like the motion sensor or night light.
I guess for a fiver (deal on here) it makes for a cheap charger! (edited)

Unfortunately not, it was answered in the Q&A on the product page and can only be used for either power or compatible with the movement detector/nightlight

Thanks Guys