RBR20-Conseils sur système à choisir

Here is a Google translation. I can read a bit of French and the translation seems reliable.

I have possible solutions in mind, but most of you know much more than I do. Note, our friend says s/he has a three-level house and that the fiber comes in through the garage. (Is the garage under the house?) I'm glad to finagle some kind of a summary in French for our questioner.

Orbi rbr20 alone or system with satellites
Hello,
 
Could you tell me which is the best solution for me? I live in a house on 3 levels
 
Arrival fiber optic in garage with modem box, TV decoder upstairs, ethernet cable connection RJ 45. I would also like to put an Orbi RBR20 to distribute the wifi in this floor. On the ground floor of this house, I have a 45 m2 apartment that I will rent to students. Is it better to put a second Orbi RBR20 there to distribute the wifi in this 2-room apartment, or else a system with base in my living room + satellite rental part, not knowing if the connection will be good (concrete slab and distance about 10 m). The rental part is wired with RJ 45 from the garage (modem box).
Thank you for your answers
 
cordially