@BrianTX,

The AXE300 is capable of achieving much higher speeds than what you showed. One thing I would make sure of is that you were connected to the 5Ghz network, if not you could try disabling the 2.4Ghz network.

So for some First Steps:

Try altering the QoS settings for your router; if the automatically obtained values are incorrect, this could dramatically affect the speed.

I would potentially look at changing the default DNS server of the router to a common service, such as Google or Cloudflare. Depending on your location, you may see an increase in the overall speed, but it should never be as dramatic as this. Never Hurts.

Try performing a speed test while over a wired connection to the router, just to make sure that the router is reading the WAN connection as 1000Full.

Also, make a point of looking at the link rate or speed that is listed in either the network settings or the properties for the network adapter; this is the maximum speed that your device would be able to communicate with the router based on its hardware properties. 

Lastly, the AXE300 has I believe 3 Different WAN options when it comes to ethernet ports; I would recommend not using the port tied to the SFP module and seeing if the speed remains the same.

  @BrianTX,

Sorry, missed the fact that you had mentioned it was in AP mode.

A few things,

Have you checked the link speed for the network adpaters on the device these tests are being run? The realistic speed is usually calculated using the link speed of the client, rather than what the router is able to send over a connection. If the devices have gigabit adapters and the link speeds show as 1000, you are well within the expected range even though it can go higher. The rule of thumb is that you are only going to be able to receive 30-60% of the client's link speed. This is why the quality of mesh connections can increase so much when the nodes are wired together, rather than wirelessly connected.

If you have the previous AP that you had used, you may check the settings that were used for the wireless network to see if these happened to be the golden settings for your connections.

For devices that have previously experienced slowed connections, it has been recommended to try and set the 80MHz width and to channel 36 to see if the speeds are increased.

Unless it is needed, you may want to try turning down the transmit power to see if it has an affect on the signal speed.

Lastly, make sure that you are using the most up to date network drivers on the devices that you are testing; it is possible the AXE300 has additional requirements for high speed connections than the previous AP did.

  @tc0566,

While the adapter is definitely capable, that does not mean that the link speed between the adapter and a network will always be the same. It's even possible that an older Ethernet Wire could have a fault that causes only some routers or clients to establish the correct negotiated speed.

While it's different because it involves hardware, think about the link speed that is established during port auto-negotiation. If one of the devices is perceived as not being compatible, the link rate could immediately be cut in half if the router chooses half-duplex rather than full-duplex.