I was ready to buy a new adapter but since many in the same class have the same chipset, Realtek RTL8812AU, I figured it might be likely that they would have the same issue so I decided to try hard to fix it.
Here's how I fixed it:
First download the http://www.tp-link.com/us/download/Archer-T4U.html#Driver
This gave me: ArcherT4U(US)_V2_161129_Windows.zip with a "Windows 10 64bit" folder inside. This step is important, you don't want to be stuck without internet and have no driver.
Windows Key + x go to "Apps and Features", find the tp-link driver and utility and uninstall. I rebooted.
NOTE: A little scarily, after doing this I could not get the adapter to work. Going to device manager and right clicking on Network Adapters and choosing Scan for hardware changes would show the adapter with the yellow exclamation and right clicking and choosing Update driver and letting windows search OR browsing for files and saying search for drivers in this location would not work. The device is supposed to be plug n play on windows 10 but removing and re-inserting the adapter, uninstalling from device manager, and disabling/re-enabling would not get windows to "plug n play". In contrast when I first got it, it worked out of the box.
- The key was right clicking on the device in the Device Manager, choosing
Update driver, choosing Browse my computer for driver software, Let me pick from a list of available drivers on my computer, Have Disk, browsed to my ArcherT4U(US)_V2_161129_Windows folder I download earlier and chose the "Windows 10 64bit" folder and hit ok.
After doing this I had connectivity again and my speeds were back to normal!
The below article gave me the idea to uninstall the driver and reinstall because of possible corruption. Microsoft rep mentioned:
There are chances that some driver files are getting corrupted when
updating our system
https://answers.microsoft.com/en-us/windows/forum/windows_10-networking/windows-10-creators-update-wifi-very-slow-problem/ff4c9f4a-f7f8-443a-932c-30603066e925