For those interested, here are my settings which give me a fully solid 60fps with perfect frame pacing (No micro-stutter).
MY PC Specs:
Ryzen 3800X (No OC)
Asus Rog Strix RTX 3080 (+70 core, +750 memory OC) NOTE: Approximately 1.5 FPS gains over stock clocks so not a concern
16 GB GSkills Trident 3600mhz CL14 memory
PCIE 4.0 M.2 NVME (Seagate Firecuda)
240mm CPU AIO Water Cooler
Nvidia Control Panel:
-Power Mode: HIGH PERFORMANCE
-Low Latency: ULTRA
OPTIONAL: Enabling Anisotropic Filtering 16X in the Nvidia Control panel looks better on flat textures but I get a slight, but noticeable flicker when I do it. Either way enabling or disabling will not impact performance in any measurable way vs in-game settings.
-Full Screen Optimization: DISABLED (Find .exe file, right click -> Properties -> Compatibility -> check 'Disable Fullscreen Optimizations -> hit 'Apply')
-Hardware Accelerated GPU Scheduling: ENABLED
NOW RESTART YOUR PC BEFORE CONTINUING
RivaTuner Statistic Server (RTSS)
Set Frame Cap: 60
In-Game Display Settings:
Frame Cap: OFF
In-Game Graphics Settings:
All MAXIMUM/ON except:
Volumetric Clouds: HIGH
Motion Blur: OFF
Depth of Field: LOW or OFF (Low sees a +0.5fps improvement on average over OFF)
NOW RESTART THE GAME EVEN IF IT DOESN'T TELL YOU IT NEEDS IT
With this setup I get a rock-solid 60fps that only ever dips during loading screen to cutscenes or sometimes autosaves.
These settings also work perfectly fine at true 4k but you will see somewhat infrequent dips to low 50s when a.) entering large cities, b.) charging the shoreline during a raid, c.) sometimes during dialogue cutscenes, d.) randomly if lots of character models are onscreen. Due to the RTSS cap of 60fps when you do get dips below that it will hitch pretty badly so I recommend sticking with 1836p, or if you simply must have 4k set the Rivatuner frame cap to 50fps and the turn off the frame-counter so you don't have to see it and just know that it's probably fine. Or disable the frame-cap and live with the stuttering. This post is more about getting solid frame-pacing at 60fps with the best possible settings than getting a playable true 4k experience.
Hope this helps out a few people.