I'll go against what most comments said and recommend DirectX 11. Yes, DXVK will translate it to Vulkan anyway, but Larian's own Vulkan implementation is definitely less stable compared to DX11.

I've experienced multiple crashes during simple things like opening the character sheets using the tab key, or crafting alchemy potions. I never had a single crash using DX11. I used Fedora 39/40 and openSUSE Tumbleweed, so the kernels were fairly recent. Radeon 7800 XT GPU.

I had the same experience under Windows 10 (before I switched to Linux), Vulkan has smoother frametimes but DX11 is more stable.

YMMV, this is just my experience from almost 400 hours played so far.

Directx 11 in this case, played bg3 on Linux and that was the only option that worked, and it did work quite well.

As for when to use one or the other, just check protondb. People usually leave what they played on, they even leave some useful launch commands or solutions to issues that could possibly arise, so it's always worth a look.

Always is better to use vulkan!