So on all my builds I'm running max (RT lumen included). The only things turned off are the usual post crap. For a while I was trying DLAA, forced via NV Profile Inspector, and the opening dungeon stuff was well into the 90-100 FPS zone but once I reached the surface I saw both rigs hitting 40-50 FPS in different spots. This also aligns with at least one pro review I read at one point which spoke how this game could pull a 5090 down.
Also had MFG set to 3x, this is what I normally use all the time these days when able.
So next step was to set to DLSS to Ultra High Quality in NVPI, 77% instead of High Quality (either 60% or 66% I don't remember which). This isn't a preset available in games but you can find in the drop-down box in NVPI. This combined with 3x MFG produced 110+ FPS. However extremely noticeable traversal stutters happen here. Try running for long distances above ground and they occur semi-regularly about every 5-10 seconds. This is the most noticeable scenarios to produce them and its pretty bad.
However, limiting FPS to anything between 70-90 really cuts down on this. I believe the original engine just can't deal with 100+ FPS. Ultimately I have all my rigs set to 70 FPS for this game and TDP/temps are insanely low while rendering is very smooth. System TDP on the 9800X3D/5090 rig rarely exceeds 330W.
From the 5800X3D/5090 to 9800X3D/5090 @ 4K and then the Ultra 275HK/5090 Mobile in my laptop @2500x1600, all three rigs performed similarly with these settings.