Configuring Orbi AX4200 with AT&T fiber

Need help configuring my mesh system with at&t gigabit fiber and 24port gigabit switch. Some basic info:

Orbi Wifi6 Mesh System - AX4200
AT&T Router - 2Wire 5268AC
TP Link Unmanaged Switch - ‎TL-SG1024S

Basically, I have the wifi disabled on the at&t modem/router, the Orbi is running in DMZ mode. I have the switch coming off the modem, and the orbi is connected to the switch.

All stationary devices(TV's, game consoles, NVR etc.) is connected to the switch, while all mobile devices(phones, tablets, laptops, smart devices etc.) is connected to the wifi.

My issue is that ALL devices seem to be running very slow. When I run a speed test on wifi, I'm showing ~940Mbps which is good. If I connect a laptop hardwired, I'm showing about the same. When I run a speed test through the Orbi app, and when I run a speed test through at&t app, I'm showing similar numbers. However, all of the TV's in the house are buffering way more often than they should. When I play an online game, I'm getting pretty significant lag. When I try to load webpages and email services on our laptops, it takes way longer than it should. Downloads on game consoles or app downloads on phones or TV's rarely show speeds above 100Mbps...

Since this is happening both hardwired and wireless, my thought is that there is configuration issue with how the router and modem are setup. Any help would be appreciated. I've spent way too much money on this setup, and per month, to have noticable lag in games or slow downloads.