So here's the situation. i'm running Comcast Gig speed into there XB7 modem, which is connected to my desktop via a Cat 6 cable from the 2.5gb port into my motherboards 2,.5gb port.

With nothing running, I can pull 1200mbps down all day long on any speedtest site, but the second I stream one 10800P video, which according to task manager is pulling around 10mbps, my speed drops to 300 or lower when running a speed test. if I stop the stream, goes right back to 1200mbps.

Running a speedtest over WiFI via my iPhone 12, I can pull 700-800mbps all day long, even when streaming on my PC and my speed drops to 300 on the desktop. I'm running the latest driver for the Intel i225-v, but it happens regardless of what I install.

I'm at the end of my rope here on how this is possible, even more so after seeing how my WiFi devices are uneffected...

Specs:
Core i9 10900K
Asus Strix Z490-a
32Gb RTam
RTX 3080
Windows 10 20H2