"Performance is terrible (slideshow)." Solution: You may have accidentally forced WARP. Go back to Device Settings and set Driver Type to "Hardware" instead of WARP or Reference.
Even with the "full" emulator, you will encounter errors. Here is how to fix them: dxcpl directx 12 emulator full
If you need to use the tool for diagnostic purposes or to bypass a launch error: "Performance is terrible (slideshow)