Steam > Unturned Properties > General

-NoDeferAssets -UseLevelBatching=false -force-vulkan -ScrollViewSensitivity=4

-NoDeferAssets
Disable the deferring of loading vehicles and level objects until map load time, and instead load on startup.
-UseLevelBatching=false
Overrides whether level batching can be enabled. By default batching is disabled but it can be used for safety reasons.
-force-vulkan
Force Vulkan. You can also try "-force-glcore" that force OpenGL but Vulkan works the best for me.
-ScrollViewSensitivity=4
Multiplier for uGUI scroll view distance travelled when rolling the mouse wheel. Change number if it's too fast for you.

-width
Or just "-w" override in-game resolution width.
-height
Or just "-h" override in-game resolution height.
-RefreshRate=
Monitor refresh rate override.
-Glazier=
Use a different UI system instead of the default uGUI. Accepted values are "-Glazier=IMGUI" (legacy) and there is a expreimental UI but it don't work well "-Glazier=UIToolkit"
-FrameRateLimit=
Overrides the frame rate limit specified in the display menu. Negative values disable the limit. Useful if game is running at thousands of FPS on the loading screen and overheats.

Display
Exclusive for better performance / Borderless for faster "alt tabs"
When using -force-vulkan there is no difference in "alt tab" speed.

Graphics
Highlighted values stands for worse performance but some visuals
when using . that don't change "alt tab" speed

Max Draw Distance: 75%-200%
Nerby Draw Distance: 50%-100%
Landmarks: Off / Medium
Landmarks Draw Distance: 75%
Ragdols: On / Off
Debris: Off
Ambient Oclusion: Off / On
Bloom: On
Film Grain: Off
Terrain Transition: On
Grass Displacement: Off
Scope Focus Foliage: On
Blast Marks: On
Rain Puddles: Off
Snow Glitter: Off
Triplaner Mapping: Off
Skybox Reflections: Off
Item Icon Anty-Aliasing: Off
Chromatic Abberation: Off

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Anty-Aliasing: Off / TAA
Anisotropic Filtering: Off / Forced On
Effect Duration: Low
Grass Density: Low
Sun Shafts Quality: Off
Lighting Quality: Off / Ultra
Screen Space Reflections Quality: Off
Water Quality: High / Ultra
Planar Reflections Quality: Low / Ultra
Scope Quality: Low
Outline Quality: Ultra (It's up to you. Look at the item on the ground and check difference.)
Terrain Quality: Low / Ultra
Wind Quality: Off
Tree Quality: Basic Trees (It's up to you. Some maps have a custom trees that you can't change.)
Render Mode: Deferred

Steam > Unturned Properties > Install Files > Browse

Open Preferences.json and change "Use_Skybox_Ambience": to true

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I took commands from here:
https://docs.smartlydressedgames.com/en/latest/about/launch-options.html#game-options