RBR850 - Access Point + wired backhaul & security issues

Hi all,
Thank you for all your help!

First a practical remark: it is not very easy to do something about my cable-setup. All devices mentioned are in different rooms (often different floors) and e.g. installing an additional network cable that goes directly from my RBR850 to my RBS850 would involve drilling some holes in walls and ceilings. This is a scenario I would like to avoid (then I prefer two cheaper non-mesh access points instead).

Some more input on the devices involved:
* My switch is an unmanaged switch (Cisco SG102-24 Compact 24-Port Gigabit Switch)
* My router is a Fritz!Box 7590, which is connected to a cable-modem, a CBN CH6643E (provided by the ISP);

A direct link between the ISP modem and the RBR, as suggested by FURRYe38 is also not possible. First of all, the router needs to be in between. Secondly, my cable setting does not allow it (all cables from all rooms in the house go to one central location where my switch is. From there, it is connected to the router, which is connected to the modem).

And also the scenario where I would connect the router to the WAN port of the RBR850 and the switch to the LAN port is not possible, because they are not in the same room.

An overview of the scenario's I have tried + outcome.

Scenario 1:
Setup:
* Orbi Router (WAN port) -> Switch -> Fritzbox Router
* Orbi Satellite (LAN port) -> Switch -> Fritzbox Router
Outcome:
- Satellite is not listed in "attached devices" => no mesh;
+ All Wifi SSID's are secured;

Scenario 2:
Setup:
* Orbi Router (LAN port) -> Switch -> Fritzbox Router
* Orbi Satellite (LAN port) -> Switch -> Fritzbox Router
Outcome:
+ Satellite is listed in "attached devices" => mesh;
- The 5Ghz network broadcasted by the satellite is unsecured;

Scenario 3:
Setup:
* Orbi Router (WAN port) -> Switch -> Fritzbox Router
* Orbi Satellite (LAN port) -> Orbi Router (LAN port);
(for testing purposes - not able to have this as a final setup due to impractical cabling)
Outcome:
+ Satellite is listed in "attached devices" => mesh;
+ All Wifi SSID's are secured;

Scenario 4:
Setup:
* Orbi Router (LAN port) -> Switch -> Fritzbox Router
* Orbi Satellite (LAN port) -> Orbi Router (LAN port);
(for testing purposes - not able to have this as a final setup)
Outcome:
+ Satellite is listed in "attached devices" => mesh;
+ All Wifi SSID's are secured;

Scenario 5:
In this scenario, I introducted an additional switch ("B"), right next to the RBR850. Consider this the "think outside of the box" scenario.
Setup:
* Orbi Router (WAN port) -> Switch B -> Switch A -> Fritzbox Router
* Orbi Router (LAN port) -> Switch B -> Switch A -> Fritzbox Router
Yes, you saw that correctly, two cables from the RBR850 to the same switch!
* Orbi Satellite (LAN port) -> Switch A -> Fritzbox Router
Outcome:
° Not sure if it was mesh (see later);
+ All Wifi SSID's are secured;
So far, so good. However, some downsides:
* The network became very slow, even the wired parts. I also noticed that the RBR850 got two IP addresses assigned by the router. I'm guessing the router was working overtime trying to figure out what was happening.
* The GUI of the RBR850 became unreachable (I tried both IP addresses). So I could'n check "attached devices". However, there was a nice handover between both devices when I was walking around the house. So I guess I have mesh.
* The GUI of the RBS850 was accessible only if I was on the wifi of the RBS850. There I could verify that it could see the RBR850 and the both 2.4Ghz and 5Ghz wifi signals were secured.

For now, I'm reverting back to scenario 1.

The way I see it, is that this is something that can be solved in the next Orbi firmware release.