If you've been having Inconsistent speeds on your AC1300 Wireless Adapter you're not alone. I'd like to argue that the wireless card is excellent and the drivers are the only faulty thing. I recently switched from the default drivers to this one https://drivers.softpedia.com/get/NETWORK-CARD/Broadcom/ASUS-X99-DELUXE-U3-1-Broadcom-WLAN-Driver-7-35-317-1-for-Windows-10.shtml . Download these drivers to unlock the full potential of your wireless card! (cheesy, I know)

Here are the steps to install it:

Open Device Manager
Expand "Network adapters"
Right click "TP-LINK Wireless Adapter/Broadcom 802.11ac..." (depending on whether you have ever updated the driver using device manager before)
Select "Update Driver"
Select "Browse my computer for driver software"
Select "let me pick from a list of available drivers on my computer"
Select "Have Disk" located on the bottom right
Select "Browse"
Navigate to the folder which the drivers extracted and once in the "Driver Files" folder double click your Windows version (in my case "Windows 10 64bit) and then select the "bcmwl63" file.

After doing this I consistently exceeded the download speeds I pay for and and upload! (Keep in mind this was only on 5g. 2.4g improved, but not nearly as much as 5g speeds did.) Download graphs went from spiky to almost perfectly flat as seen below. I hope you have as much success as I did! :)