@MeshHead 

I would not trust that test in Deco lab app. I ran it in my house, which gets only weak signals from neighbors' WiFi networks, and it also claimed high interference. When I look at chart in the test I see that my Deco 5GHz channel, which is currently 36 for my Deco mesh, is "clogged" by WiFi signal from Deco units all broadcasting on that channel, and nothing else. While adjacent channels are interference-free, as nobody broadcasts on them. 

I am thinking that if can I move my Deco mesh to a different channel, the outcome of the test won't change: that new channel will have high interference. 

I have gigabit Internet. In my speed tests for Deco M5, in near perfect conditions I can set, I am getting top WiFi speeds of 460Mbps for Main and Satellite M5 wired to the Ethernet, 225Mbps for Satellite M5 connected wirelessly. 

If you want better WiFi speeds from Deco mesh, you should replace M5 with M9 Plus. In my tests I am getting WiFi speeds of 635Mbps on Main Deco M9 and 490Mbps on Satellite Deco M9.

If you want speeds closer to gigabit on mobile devices that support WiFi6, you should consider X-series of Deco units, and only tri-band ones: X68 or X90. They will cost you, but this is the price of higher speeds.

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If you truly believe there are better WiFi channels than one Deco is using, run in Deco app "Network Optimization" or "Reboot All" Deco units. In both cases Deco is supposed to rescan area and move to a different less congested channel if it can find one.

@Alexandre. that's a good point actually. No matter what channel I try, there will be five of my own networks there, so therefore always congested. That makes that test a little useless unless you are in a built up area with +++ other networks I suppose.

I think I can do more to improve the quality of the connections between units by moving them around a bit. I don't want to pay for a whole other setup until I have exhausted all options with M5 first.

What are the near perfect conditions you have achieved, may I ask? Any tips?

MeshHead wrote

What are the near perfect conditions you have achieved, may I ask? Any tips?

@MeshHead 

This is how I ran speed tests on my Deco, to find the best it can do.

Moved Deco to basement of my house, with thick concrete walls, to add protection from external wireless interference.

DIsabled 2.4GHz on Main Network to avoid Deco steering wireless device I run speedtest on away from 5GHz. Ran speed tests on 5GHz network only.

Used WiFi analyzer app to see what other WiFi networks reach my basement. Found just one on 5GHz, with signal strength of -90 dBm (very weak). That means very little WiFi interference from neighbours.

Verified I have full three bars in Signal Source for Satellite Deco my wireless device is connected to. This means good to excellent WiFi backhaul connectivity between Satellite and Main Deco.

Ran speed tests late in the night to reduce solar radiation interference and interference from household appliances such as microwave.

Ran close to 100 speed tests in that configuration. Saved best results.

@Alexandre. excellent thank you!

To get three bars, do you have line-of-sight between each Deco? What do you find impacts the Deco to Deco strength the most?

I have a two storey house with usable attic space. There's one Deco at front door connected to main broadband box, one on the first floor in our bedroom, and one in the attic. That covers the vertical levels.

Then horizontally on ground floor there's another in the kitchen (ground floor, same level as Deco at front door), and another in the office which is in the garden.

Distance between front door Deco and kitchen Deco is about 12 meters (almost line-of-sight), and from kitchen to office is about 6 meters (full LOS), however the most I ever get is 2 bars. :(

@MeshHead 

Two bars should be good enough. I needed three bars for testing purposes, to figure best Deco performance. I moved Satellite closer to Main to run tests.

In my daily Deco mesh usage, how I placed Deco units, I am getting between 2 and 3 bars on wireless Satellite Deco.

Distance, walls, electronics and WiFi from neighbors impact Deco to Deco communication. I have Main Deco in the middle of the first floor, it covers all floor with WiFi 5. I disabled 2.4GHz completely.

Right above Main Deco, on the second floor, there is Satellite Deco which provides coverage for the second floor. It reports sometimes 2 and sometimes 3 bars in Signal Source to Main Deco. That is good enough for needs of my household.

@Alexandre. thank you for your time advice Sir!