Hello @mohammadsingy, this is a general system config issue more than it is an issue with Proton. The issue you've described is that Dark Souls is running in an environment that has the integrated GPU configured to be prioritized over the discrete GPU. Other Vulkan applications are most likely affected in the same way.

There are several ways to control what GPU a game is able to use with environment variables. On Mesa's side you can use DRI_PRIME (https://docs.mesa3d.org/envvars.html#envvar-DRI_PRIME) and MESA_VK_DEVICE_SELECT (https://docs.mesa3d.org/envvars.html#envvar-MESA_VK_DEVICE_SELECT). Alternatively, you can filter GPUs used by DXVK with DXVK_FILTER_DEVICE_NAME (https://github.com/doitsujin/dxvk#device-filter).

It's recommended to set that on a per game basis as needed by going to the per-game properties, and adding the environment variables you want to tinker with to the game's launch options followed by a single %command% afterwards.