Thanks
@troop231 for this hardware update. As soon as I received it a month ago, I brought it to my local Mac repair replace specialists who removed the stock WiFi hardware and put in this one for a fee as I don't have the required tools. I had to show them the instruction and run it through with the guy who asked "What do I do with the fourth wire? Are you sure it's compatible? You won't have BT!" while I explained that it's built-in as a radio rendering it unnecessary.
In the kid's room, it managed 575Mbps. In the dining where it's closer to the router, it's as shown in the screen cap attached. Router model is Asus RT-AC68AU (N600,AC1300).