Still kinda curious as to why my max speed is 300. All cables are good.

After beating my head against the wall. I finally used a different patch cable. Go figure. Guess you get what you pay for from Monoprice. As per the test, the main computer is on a gb link to a Unifi switch and is definitely working right. I was using iperf3 from a laptop (gb also) to the main computer. It was the stupid cable from the laptop to the GoCoax unit. The last thing you try right? I guess I used a different cable for the initial check after install. The bad cable was brand new. Who knew? I should have realized that it looked like a 100 mb (95 or so) connection which is a lot of times a bad wire on a cable. This gocoax unit goes to another unify switch. Every device connected to the switch was getting the higher speeds but hard to tell when most of them are cameras and work just fine at 100mb. Just the laptop with the bad cable was screwed up.