Thank you for your kind answer,
I've found a detailed photo of what I wanted to buy, it has micocontroller, probably to manage the relay depending what coming from wifi, so I suppose I can't manage directly wifi by Arduino.
I wanted ask infos about this board because there is one in the next shop, and I don't need to order it from China.
The mistery is why it has TX and RX, what for? Maybe to program the local microcontroller? Probably
Yes the model you suggested has the 5/3.3 adaptor..