Hi @Bruenor and @McDx [again :)],
I answered this question from McDx in another thread but I will post my response here also:
I can understand your confusion when it comes to wireless speeds as there are so many factors at play. Also, thank you for providing so much detailed information.
The 433 mbps Speed you are seeing is called your Link Speed. The Link Speed is the theoretical maximum bandwidth for only the connection between your router and your computer. This is not indicative of the speed that you will actually see when working with files on the internet. This is only the speed that would be capable when moving data around within your own internal network.
The speeds that you are receiving when running a speed test, are the speeds that you are receiving into the router from the outside internet. That test is completed by sending information from your router to a server hosted somewhere else. This is also the speed that you are paying for from Cox and will vary depending on what service you use to test, and the location that you select. This is the 400 mbps speed test result that you got form speedtest.net. This means that you are getting what you are paying for from Cox.
This overall speed will be split up by the router depending on various factors such as how many devices are connected, interference and others.
If you would like to learn more about the difference between Link Speed and Wifi Speed please check out this link:
Why Isn't my Wi-Fi as Fast as Advertised?
Feel free to ask any other questions you may have! I would love to find more ways to help our customers understand our products.