I want to cover two floors With many of the rooms house with garden what do you advise me to buy the devices
Appropriate and intena؟

whate the best rb711ua2hn or rb751u or others?

thanks in advance

Wireless is a little more complicated than this, and we would need more detailed information about the characteristics of building that you are trying to cover.
For example of the walls are abnormally thick or the house is just large in general, you may need to consider more than one access point.