I have the same set-up: Internet modem plus NAS and network printer in the basement. Via ORBI, the connection to the ground floor and upper floor works without problems (concrete ceilings, underfloor heating...poison for any WIFI). Mostly almost 100% of the modem performance upstairs (500MBits/50MBits). Placement of satellites was a bit of try-and-error until it worked really well. But already first try was 10 better than Powerline or old router (Nighthawk X4S).

I confirm the above statements, also works in the basement.

I confirm that with an Orbi on each floor, concrete ceilings have no effect.

We also have strong concrete walls horizontally and finally I have network everywhere. A friend also uses rs from the basement and has had reception since then too. I am satisfied!