Works correctly here with pair of 1080 Ti under Vulkan API with no argument in R* launcher under
Hotfix Nvidia drivers 442.37 i vsync the game at my max framerate 60fps on a 2160p monitor.
i apply a bit OC to both cards to push a bit to 2012 to 2025 Mhz & VRAM +400 Mhz.
Make "pipecache windows" sga files cleans in "W10 documents folder" starting by DX12 reconstruction, then change to Vulkan API.
Restart game under Vulkan and get back your graphicals settings.
Sometime i see that vulkan is bit buggy like i see "fpsmonitor" with a bit of overlay
clipping (like right after alt tab or something ) and its a sign ;)
i go ingame parameters and switch to "Bordeless" mode (validate) and then return to "Fullscreen" mode (validate) (its like a SWITCH to me) and i see overlay clipping disappear & the game return to smooth (feel it directly when moving your character and camera moving).
i do some test with "asynchronous" compute mode or not but i didn't feel any improvements when activated.
Share my graphicals settings if its help.
Resolution: 3840x2160
Fullscreen
Vsync: On
then all off
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Texture quality: Ultra
AF: 16x
Lighting: Medium
Global illumination: High
Shadows: High
Far shadows: High
AO : High
Reflection: Medium
Mirror: High
Water: Custom
Volumetrics: Custom
Particle: High
Tessellation: High
TAA: Off
FXAA: On
MSAA: Off
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API: Vulkan
Near volumetric: Low
Far volumetric: Medium
Volumetric lighting: High
Unlocked VRR: No
Particle lighting: High
Soft shadows: Ultra
Grass shadows: Medium
Long shadows: Yes
Full res SSAO: Off
Water refraction: Medium
Water reflection: High
Water physics: [2/4]
Resolution scale: Off
TAA Sharpening: [0%]
Motion blur: Off
Reflection MSAA: Off
Geometry LOD: [3/5]
Grass LOD: [6/10] or [5/10]
Tree quality: High
Parallax occlusion mapping: Ultra
Decal: Ultra
Fur: High
Trees Tesslation : Off
Adding a bit adaptative sharpen by nvidia 3D settings parameters & a bit "clarity" from Freestyle & stew is cooked ;)
Tested over 40 hours online playin you will experience "sometimes" right after loading a white light but it will disapear, one time on moonshine mission start up light stay (just use the "switch" to solve this), and ponctually some top water textures disapearing quick but its definitively not a game breaker.
Hopes its help.
Cheers