On my initial analysis of the extender I added to my Xfinity gig network, it appears that unless you have absolutely bad to no signal, this device actually slows down devices attached to it.
It integrated fine, then I moved it half way between the router and needed destination. I connected to the ext wifi network with phone, then fired off Tether. The app suggested I could actually move it further away from the router, if I wanted. Anyway, before attaching to the new _EXT network, I ran an Xfinity based speed test on my phone, attached on the main wifi network. Standing right next to the Extender, the test clocked in at 490Mbs. Running the test again, this time attached to the _EXT network, it clocked in at 182Mbs.

The whole house network was fairly idle, with no video,/audio streaming or gaming, at the time of tests.

This is actually slower than the needed destination, which clocked in at 209Mbs on the main network.

The test from the needed destination through the _EXT network, clocked in at 130Mbs.

Since the Latency was 22ms & 19ms respectively for main and ext networks, this hardware appears to be under performing.

TP-Link Specs say 2.4Ghz - 300Mbs ;  5Ghz - 867Mbs

And yes, I was attached as a 5Ghz Client on the _EXT network. I even disabled the 2.4 port connection to the main router.

I hope I don't have to supply screenshots, to make my plea for hints/tips/explanation.

Thank You.