Wi-Fi Speed on Apple Products Dramatically Slower Than on Windows PC

Internet provider speed (Spectrum) is 500 Mbps. My wife's Surface PC shows 400-plus Mbps on a Speedtest. My Apple products (iMac Pro M1 with 64 GB RAM, iPhone and iPad barely register 90 Mbps, sometimes as low as 40 Mbps. Already reset router, rebooted Apple products, spend 40-minutes with AppleCare rep, who indicated that there's nothing wrong with Apple hardware. All hardware (Apple and Surface) next to each other and tied to same network. Slow speed results in slow and/or frozen uploads and screens, poor Zoom performance, etc. Any help is appreciated!