I'll probably make this into a separate thread, but for now here's what I've worked out as "optimized" settings.
MSAA - 4x
Filmic AA - Cinematic
FXAA - Enabled
AF - Ultra
Texture Pool Size - Ultra (I can't test this as well as I'd like because the game appears to use (or at least reserve) a lot of video memory regardless, however, if you have an 8GB card I'd recommend going no higher than "Medium" here at the moment.
Level of Detail - Ultra
Experimental Static Level of Detail - Off (I can't discern what it changes yet so I'll leave it off until I can pinpoint it)
Static Level of Detail - Greyed out for reasons above
Vehicle Level of Detail - Ultra
Global Illumination Update Frequency - Ultra
Ambient Occlusion - Medium (No discernable/obvious changes on any setting higher)
Volumetrics - High (Placeholder setting, can't seem to find a reliable way to test)
Environment Reflection - Ultra
Car Reflection - High (There's a perceptible difference in reflection clarity and resolution when going up to "Ultra", however, there's also a perceptible performance drop
Shadows - Ultra
Experimental Sim Shadows - Off (For similar reasons to Exp. SLOD)
Sim Shadows - Greyed out because disabled
Screen Space Shadows - Full Resolution
Grass Density - Low (There's absolutely no difference in anything higher than this, I reckon this isn't working as it should)
Clouds Quality - Low (There is an ever-so-slightly apparent difference in the higher settings but you'd have to zoom in to see them, so leave this on low and you'll never notice anything. Alternatively, leave it on "Ultra" for the very same reason as it doesn't incur a performance cost)
Post Processing Presets - Personal Preference
Motion Blur - Personal Preference
Mirrors Mode - Multi (This is another personal preference setting, if I'm being honest)
Mirrors Resolution - Medium (As the game is right now, there's no need for anything higher outside of eye candy; once MP rolls around you can safely max this out)
Mirrors View Distance - (Haven't tested this with a full grid but it's literally just Render Distance through the sideview mirrors)
Optimized Rendering - On (You like performance, right? Of course you do, that's why you're reading this)
Mirrors Capture Mode - Dynamic (Another personal preference setting)
I'll come back to this again once I've finalized everything but this is what I have at the moment. For reference, I'm running with a 5800X with PBO enabled, 16GB DDR4 and a 6900XT