I have a AT&T Gateway model BGW320-500 it is a modem and router in one for my Fiber Internet. I get 500Mbps speeds with it one WiFi and cable. I wanted to use a full router instead of the gateway. I so I bought the TP-Link AXE5400 Tri-Band Wi-Fi 6E Router model AXE75. The AT&T BGW320-500 Gateway does not support bridge mode so I used IP Passthrough and disabled the gateways WiFi. The issue is I am getting much slower WiFi speeds using the router VS the gateway. I setup the router and with all the settings set to default. I get around 200Mbps but when I use the gateway I get 500+Mbps. My device is Tri-Band compatible but no matter what band I use doesn’t come close to the gateway speeds. How should I set the router up and settings to get maximum speeds?

If this is a Super duper expensive router I would think it would work better. I tried router mode and AP Mode. My device is two rooms from the router and gateway but the results are the same the router is still significantly shower. Why