Tinkering steps: Create a dxvk.conf file with the settings reported by other users, adapt them to your GPU. I'm using a 1080 TI with 11gig vram, my settings are for 10 gig (10240 mb)
In Lutris, go to your battle.net settings -> System Settings and add the environment variables:
key: DXVK_CONFIG_FILE value: /path/to/dxvk.conf
key: PROTON_HIDE_NVIDIA_GPU value: 1

Set graphics quality level to medium