Windows 10 too slow after adding 4k monitor and disabling DirectX

[WonB]

My Windows 10 is now too slow after adding a 2nd 4k monitor and disabling DirectX.
(I had to disable DirectX in order to fix a different, screen-related issue. https://forum.parallels.com/threads/windows-10-screen-distortion.339105/)

By "too slow", I mean that screens are slower to move around, sometimes typing is lagging, and even web pages are slower to load.

What can I do to improve the situation?

 

[PaulChristopher@Parallels]

Hello WonB, are you connecting via thunderbolt adapter? If so, please change the network type as follows virtual machine configuration->Hardware->Network 1->Bridged ->Thuderbolt or simply choose Shared network mode.

 

[WonB]

I don't use thunderbolt adapter. But changing the option from Default to Wifi, which is what I'm using, seems to have helped.
I still have other screen-related issues, such as flickering, but I'll deal with them in a separate thread.