ORBI RBR50

This is a complicated situation.  An Orbi "router", i.e. RBR50 cannot be a satellite.  iI just cannot.  If it is wired to an Orbi router, it will create a separate WiFi network of its own.  You can give this new network a network SSID and password identical to the primary router, but they will not become "one system."  Never.

So, yes, it is a great idea to locate an access point in the garage close to the Ring doorbell, and hard wire it to the Orbi router.  Your second RBR50 can be configured to be an Access Point (AP) on the Orbi web interface, Advanced Tab, Advanced Setup, the second menu item "Router / AP Mode".  You could also use any old access point you have lying around and wire it into the Orbi router.

Many of us are frustrated (and mystified) that Netgear created what appear to be identical units (RBR50 and RBS50) and "locked in" their functionality.