Your guys should feed it back to TP-LINK support team instead of complaining here as it will push them to release newer firmware with features what you need more quickly....

Go to Asus website and download the driver of AC68 which uses the same chipset as T8E for Windows 10. Try to update that driver. It might help.

It is very frustrating and disappointing indeed but I believe TP-LINK is pushing their chip manufacturers to provide drivers for windows10 as soon as possible. If it is quite urgent, it is reasonable...

But Vista W8.1 and W10 can connect to main router's Wi-Fi name and work properly? Can you update driver for wireless card on those devices?

The UI is updated indeed with the latest firmware and no firewall option anymore. Some of firewall functions can be applied with other features. But if you want to block WAN Hosts, you need to revert...