@Sheps 

TP-Link Deco mesh does work just fine in Access Point mode. I do run it that way. The guy in YouTube video is too smart for his own good. 

For Deco mesh to run in AP mode, networking gear must support Deco mesh protocols. Most switches and routers do, but on video at 1:30 you can see he is using D-Link switch, and that brand does not - this is a problem.

I stopped watching video at this point.

I suggest you start with this document: General questions about Ethernet Backhaul feature on your Deco

If you have more questions, have network diagram of how you plan to deploy Deco mesh, with switches and such - I can assist. If you plan to buy networking switch(es), I can give recommendations. 

  @Sheps 

Many thanks Alexandre.  I am glad to hear that Access Point works well with Tp-Link Deco.

I would like to take you up on your offer to assist with planning my network.  Please find attached my draft network diagram.  This is my first attempt at documenting what I am thinking of so hopefully this makes sense.  I've raised a number of question in relation to the design.  Your feedback would be appreciated.

  @Sheps 

Apologies - another quick question.  Do you know if the following are NBN compatible (Fibre to the Premises):

• TP-Link Deco X50 POE AX3000 Home Mesh WiFi 6 Router is NBN com
• TL-ER7206 -SafeStream Gigabit Multi-WAN VPN Router

  @Sheps 

To clarify: I can help with the part that is about Deco mesh running in AP mode. I have experience running Deco mesh in AP mode, also general networking experience. My ISP provided me with the Router and I can't change it.

In regard to your network diargam.

1. Unless you have preference, I would suggest to go with unmanaged switch. TP-Link brand should be safe bet;

2. You will need to calculate by yourself if power provided by the switch over PoE will be enough for two (or three if with Main Deco) Deco units; 

3. With Deco mesh in AP mode, you can connect Main Deco to the switch or to the Main Router, but not to both. Which means to either LAN 6 port on the switch, or LAN 4 port on Main Router.

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When you do initial Deco mesh setup, I would recommend to configure only Main Deco first, keeping rest of Deco units powered off. When Main Deco is up and running, switch it to Access Point mode: Switching a Deco to Access Point (AP) Mode

After that, power on Deco units that will be Satellite Deco. To avoid any issues, I recommend not to wire them to switch when you power them on first time. Place them in the same room where Main Deco is, so that they can connect to Main Deco wirelessly and complete Deco mesh configuration over WiFi.

After that, bring Satellite Deco to their permanent locations and hardwire them there.

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Also note that Deco X50-POE has two Ethernet ports. One you will use to connect Satellite Deco to the switch, another you can use to connect wired device to it. For example, I have wired network printer connected to one of my Satellite Deco, and have Smart TV hardwired to another Satellite Deco.

  @Alexandre. 

Many thanks for all your help.

FYI

I've reached out to the broader group  re the compatibility of the proposed diagram and tips on how to improve.

And with the proposed diagram whether I need a Omada Software Controller and if required the benefits of doing so.

Once again many thanks