X20 Deco Tp-Link Mesh Access Point Mode Correct Setup

Hi there

I want to confirm a few anomalies for my current home network setup, with two X20 Deco units.

Currently, my wireless router is acting as the gateway for my network, broadcasting both a 2.4ghz and 5ghz signals (as normal).
The wireless router at 192.168.1.1 is handling the DHCP.

The Deco's were initially setup with the Deco App, and changed from router mode, to access point mode.
The first Deco is connected to the wireless router via ethernet cable at 192.168.1.15
The second Deco is in a different room where the wifi signal is weak at 192.168.1.19

My understanding is that the first Deco is not an access point, but is rather a wireless bridge, transmitting internet traffic to and from the second Deco wirelessly. So, the second Deco broadcasts the router's same SSID, but as an access point. I can confirm this in the deco app, with no clients connected to the first Deco and all clients connected to the second Deco (obviously expect the clients which are closer to the wireless router).

This seems to be working, however my phone has a strange behavior, as I believe it sometimes tries to connect to the first Deco.
I used inSSIDer to check how many SSID's were actually broadcasting, and there was indeed three 5ghz (same names). In addition a hidden network.
So the first Deco I assumed, must be this extra SSID and possibly require its SSID to be on, to communicate with the second Deco.

First I want to know if this setup seems right, and if any other known information on why the first Deco would need a SSID?
Secondly, if there is anyway to turn off this conflicting SSID on the first Deco.