@plemansis correct. Using wired backhaul generally improves the speed and stability of the "backhaul signal" between the Orbi and satellites. It has nothing to do with the WiFi signals provided to client devices in terms of signal strength or coverage. WiFi radio signal strength is regulated by the FCC (or equivalent in every country). When Orbi is transmitting at 100%, that is the maximum strength signal that is possible.
Depending on the building construction, using the wired backhaul can expand the area covered for users. With 5G WiFi backhaul, as the satellite gets farther from the router, the signal falls off. That is why Netgear recommends placing the satellite where the top ring turns "blue" when it connectes, rather than "amber." In practice, this means that there is considerable overlap between the router coverage and the satellite coverage. With wired backhaul, the satellite can be placed farther away and thus "push out" the area that gets good coverage. For most of us, our houses are not large enough to need the additional coverage area.
Anyway, thank your lucky stars that this house has ethernet wiring in the walls. Use it.
