Source: https://news.blizzard.com/en-us/world-of-warcraft/21952591/the-battle-for-azeroth-pre-patch-goes-live-july-17th

Don’t Forget: Update Your Drivers!

To make the most of Battle for Azeroth and avoid potential issues, it’s important to update to the latest DirectX 12 drivers. Please note that AMD and Intel GPUs will default to DX12, while NVIDIA drivers will remain at DX11 with the option to update at a later time.