RAX80 as access point wifi slow over CenturyLink Fiber

Hello, 

How can I get the most out of my wifi?  Why can't I get the bandwidth maximum based on the service (wired connection)/connected speed of the wifi chip?

I have CenturyLink's 1Gbps (940Mbps) Fiber service, connected to their gateway/mode C3000Z in a wired home environment.  I have the connection to my SX10 switch, then to my RAX80 router that I am using in Access Point mode to provide Wifi to my home.  All hardwired connection (to gateway C3000Z, SX10 switch, and RAX80 get download/upload speeds of 900+Mbps all along the way).  However, when I try to do wireless, I am only getting anywhere from 200-450Mbps down/up.   I use the app Speedtest to test my bandwidth (wired/wireless alike).

Bandwidth I have gotten per item/chip:

•     Apple Iphone X - 314 down/450 up
•     Laptop with an Intel AC 7260 chip, connected at 866 Mbps (AC80mhz 2X2) - 250 down/300 up
•     Desktop with an Intel AC 9260 chip, connected at 1.7 Gbps (AC160mhz 2X2) - 300 down/300 up

Stuff I have tried:

•     Updated to most recent firmware (V1.0.1.70_1.0.30)
•     Did a factor restart
•     Turned on/off QOS/WMM
•     Enabled/unenabled Beamforming
•     Enabled/unenabled MU-MIMO
•     I currently have WPA2-PSA security (also tried it with no security)
•     AX is enabled, but do not have anything with an AX card to test.

Anything else you can think of, to help me get closer to the speed I feel I should (866Mbps on Iphone and Laptop, and 940Mbps on Desktop)?