I've posted this in the router thread but got no response so I was wondering if anyone here been tho the same problem or able to assist.

I am using Unifi Turbo-ed to 300 Mbps. BTU using Huawei 8240. So, happily changed my router to Archer C6. But after trying to config around, the max speed I could get is around ~120 Mbps max for WiFi (Tested on Lenovo X280 laptop and iPhone XS). Often than not it's below 100 Mbps.

LAN Cable from BTU to router I'm using CAT 5e. Are they any config that I've to set in order to reach near to 300?

Location of test: Right beside the router and BTU running on 5Ghz.

I only have 1 cat-5e lan cable, others are the old CAT 5. Tomorrow maybe I go source one cat 7 cable and then test it out via lan.