@NeilF 

In scenario you descibed, there is no benefit of running Deco in router mode, just potential headaches. 

I had similar situation: home network configured the way I want, for wired and wireless devices, but WiFi signal from ISP provided Gateway unsatisfactory weak. Bought Deco nodes, set them in AP mode to provide WiFi coverage and very happy with results. 

I expect better performance from Deco in AP mode than in Router mode, just because it would not have to do all the stuff you correctly listed it does in router mode. Parental controls and device bandwidth control do not come for free.

If you go with Deco in AP mode, I suggest at the beginning you keep your current network configuration and plug Main Deco to one of available switch ports, such as:

--internet --> [Sky Router] --ethernet--> [Switch] --ethernet--> [ALL DEVICES including Main Deco]

The reason is, when you turn on Deco first time and start configuring it, it'll be in router mode by default and may start managing your network, until you reconfigure it into AP. So, for configuring just plug it to available switch port and move later if initial setup went without issues.

Also, this:

--internet --> [Sky Router] --ethernet--> [Deco] --ethernet--> [Switch] --ethernet--> [ALL DEVICES]

reduces your home network resiliency. You will depend on Deco doing everything right all the time. It should, in theory, but just read through these forums.

Of course, if you don't plug Deco in front of everything you have on your network, you won't have realtime per each device download and upload speeds. Yes, they are reported for both AP and Router modes. Yet, after looking at that report few times I now ignore it. The report is really real time with no historical data saved, not always accurate and occasionally delayed by a second or few. 

So, you choose: network resilliency or realtime bandwidth utilization reporting. Yet, whatever you choose, Deco in AP mode is the right mode for your network with your expectations. Just like it is for mine.

@Alexandre. 

Hey! That's great help thanks!

I'll definately plug the Deco Router simply into the switch/router with nothing else attached to it just in order to configure it to AP mode.

Then I'll move it to:-

--internet --> [Sky Router] --ethernet--> [Deco] --ethernet--> [Switch] --ethernet--> [ALL DEVICES]

Later, I can shuffle the stuff to move wired elements off the Deco. eg: Move a number bits of the wired network off into the three available ethernet sockets I still have on my router, to take them away from the Deco's control.

BTW, which Deco did you go for. I think I'm down to the M5 (£150) or M4 (as newer and under £100) as my choice?

Again, thanks for the help!

@NeilF 

I went with 2-pack M9, because I needed to wall mount one of them in narrow corridor and because I knew I will utilize M9 feature, which is backhaul on separate 5GHz channel. If not for backhaul, I would have chosen M5.

My only regret is I didn't buy 3-pack, so later bought single M5 for an ideal WiFi coverage in my house, and hardwired it. 

If you choose between M5 and M4, and form factor is not important for you, consider this:

1. M4 is slower on 2.4GHz comparing to M5: 300Mbps for M4 vs 400Mbps for M5. If you plan to run everything on 5GHz or your Internet speed is under 200Mbps, you probably won't see the difference.

2. M4 should have better heat dissipation than M5, because M4 is tall tower. If you plan to tunnel all your Internet to home network traffic through Deco, like it is on your final diagram, you'll probably be better with tower device, meaning M4. Especially, if later you decide you'd rather run Deco in router mode.

My M9/M5 Decos don't get hot, but all my heavy Internet using devices are hardwired and connected directly to ISP Gateway through switches. Decos just sit aside to provide WiFi to smartphones, tablets and IoT devices. I saw someone complaining on this forum their M5 is getting too hot to touch, which is too hot, indeed. 

@NeilF Two further question if it's not too much bother:-

1) Is there a single list of devices attached to any/all of the mesh units? Or do you have to click into each of the mesh units, to look at the list of devices attached to each one? ie: If you want to see how much data an iPad is using, can you look at a single list of all devices attached to the mesh? Or do you have to click through the individual mesh units, and find the iPad in question?

2) Can you see if a device attached to the mesh is connected via 2.4hgz or 5hgz?

Many thanks again!

ps: Sorry a bonus question. Can you still create a Guest Network in AP mode?

@NeilF 

>Can you still create a Guest Network in AP mode

Yes, you can - but it does not mean what we think it should mean.

Devices on Guest Network in AP can see and can access Main Network. There is no separation between both networks.

What I am using Guest Network for is to separate WiFi bands: my Main runs on 5GHz only and Guest is set as 2.4GHz only for IoT devices that can only use 2.4GHz.

@TP-Link Excellent... So in AP mode:-

1) You can see all devices (wireless and wired) attached to the mesh as a whole, and their download/upload speed.

2) You can drill into an individual mesh unit, and see the devices attached specifically to it.

3) You can drill into an individual attached device and see its details, including if its on the 2.4ghz or 5ghz network.

And this was shown for the M5, and I assume the same is true of the M4 Deco software?

Ah, so the Guest Network is almost pointless in AP mode for its intended purpose (of being slightly more secure/easy to access). You may as well just give folks your real network name/password. OK thanks...