I found a page from TP-Link, maybe that will help.
https://www.tp-link.com/de...

The signal is quite strong, but it also depends on whether you only have wooden floors or solid reinforced concrete between the floors. If you want to buy this router anyway, I recommend doing a test without satellites first; if that's not enough, you can buy another satellite. Basically, you should then make sure that you position the satellites on the different floors one above the other if possible.