Satellite Placement and Adding Extender

I live in a narrow but fairly deep 4 story brownstone house. My cable service and modem are in the front room on the third floor, which is where the Orbi router now lives. I did not find much success putting the satellite on a different floor (most devices seemed to connect to the router and not the satellite no matter what), and so instead I placed it on the same floor at the rear of the house. That gives decent but not perfect coverage front to back, and the signal naturally is a bit weaker as I go down to lower floors.

Does anyone have a view on whether adding another satellite to a lower floor would help (or hurt), and whether it would be better to have it at the front (a floor under the router) or rear of the house (a floor under the other satellite). Could adding another satellite, while expanding coverage, impair overall speed/performance?

Any suggestions much appreciated. Thanks.