To check local wifi speed, I normally use iperf3. It require 2 device, 1 act as server and another 1 act as client. It is recommended that the server is directly connected using lan cable (cat 5e or higher) to the router/switch (and make sure it is gigabit capable). Then the client can perform the test using either wifi or lan cable.

Ax20 is gigabit capable over lan. Could be your lan cable or your pc mootherboard ethernet port that could only support up to 100Mbps

Guys regard to this setting should i just leave it like this or need special tick on which collume

okey noted , what the benefit of turn on wireless a/b/g/n?

I have warned a lot of time about this here and people still choose to buy Xiaomi or China router.

All China router designated for China market will have weak WiFi signal due to regulation.

Their transmit power regulation much lower than international standard.

Am using one main router AX20 located upstairs hall, am satisfied so far with the connection and stable speed cos sub to 100mbps. Built up approx 2800sqf

Below is the speed and connection taken while I'm at the front porch which is OK.

Would adding another AX20 or M4 (connecting to main via wifi) as mesh is worthwhile?

All dual-band mesh WiFi system will only deliver half of the total backhaul capacity at the mesh node.

It doesn't mean half of the 100Mbps speed you are subscribed to.

Let say the link speed between the mesh node to main node is 300Mbps, the maximum WiFi speed you can get from it is around ~150Mbps.

In general you do not need to test the network speed for home since it is not busy place. Network speed it to test the traffic in network.

When you device do handshake signal with AP or your wireless router, the connection is established at certain speed due to signal condition due to interference or distance. I think you can see what is the establish speed on the phone by pressing on WiFI icon or use apps. I'm sure many apps out there can show connection speed. No matter if your router can connect at 500Mbps or not, your speed will max at the establish speed 

For mesh router, it is full capable speed. The reason for reduced bandwidth is just because you use half of the band as connection to the other mesh unit. So, only the other half is available for traffic to your device.

If you use LAN cable from one mech unit to the other mesh unit, then each mesh unit will have full bandwidth to communicate with devices.

For range extender, it is not really half the bandwidth but more like half the speed. Say your router takes 1s to extender and from extender 1s to your device. Then total time is 2s. If you have connection from router to your device, then you only need 1s. So, it is half the speed, but it is like half the bandwidth too 

If streaming gives problem I guess it is not about bandwidth but the processing power of the device or perhaps faulty unit. Cheap unit tend to have slower processor thus hung up if buffer gets overloaded I think.

The difference between Deco Mesh and OneMesh has nothing to do with dedicated backhaul. When Asus came up with AiMesh, you just need to upgrade a bunch up listed models with AiMesh firmware and you can have mixed Asus model to perform like mesh network. Other players at that time you need to buy a mesh units set. If you already have one model, you have to ditch that one and replace with mesh set.

To simulate what Asus did, then TP came out with OneMesh. The Deco Mesh comes as a set of AP decicated for mesh. Therefore the OneMesh is cheaper solution. The difference is here:
https://community.tp-link.com/us/home/stories/detail/536

I do not have mesh routers but if I need to setup one, I will opt for LAN connection between mesh. The reason is simple. The connection speed between two unit related to distance and also obstructions. So, the further the distance, the backhaul speed will also suffer. You will have improved coverage but you will lose speed and not utilizing full router potential if you use wireless backhaul. You do not want to put your mesh unit near to each other right? 

I bought an Asus since it was the only brand that enable you to build mesh network stage by stage since can mix model. However, my Asus GT-AC5300 can get at least 200Mbps anywhere inside my two storey house when I run speed test. Maybe not much thing in my house 

My Unifi fiber goes under porch roof and through the wall behind TV cabinet and to BTU in TV cabinet. All hidden. I drill the hole and made preparation a day before the contractor came. So, it done very fast.

If I want to have a mesh router on 1st floor. I will route the cable the same way. Put short trunk outside the house and drill a hole in master bedroom where I can place a cabinet or shelf to put the unit. Will be nice without messy wiring inside the house. 

Yes, single router is easier. Since now everyone gone AX crazy, the AC price much cheaper. Actually the old top tier router has some feature of the AX already. The modulation even go to QPSK 1024.

I realised the problem is with the stock unifi router. Bottleneck issue. Would want maximised speed and coverage so extender and repeater is not sufficient for my usage.

I'm going for M9 Plus but now considering whether i would wanna upgrade the 842 to ax73.

Have u receive your order@ email yet? Just get upgraded today. No email yet for mesh wifi 😅

you may install wifi analyser tool to find out best spot for full house coverage

https://vremsoftwaredevelopment.github.io/WiFiAnalyzer/

Best way is to still just run a lan cable across but of course depending on the situation it might not be possible