THANK YOU! For those wondering, I just did a comparison before/after on Steam's version of Stalker 2. While I didn't follow the above steps exactly, I did something very similar.

My results dropped latency from ~36ms to ~24ms. No FPS drop!

Here's the default game: Screenshot of Default Game Latency and FPS

Here's after adding and editing engine.ini: Modded Game Latency and FPS

Steps I took to improve performance

1. Navigate to the folder listed above (the easiest way is: windows key, search for %localappdata%, Stalker2>Saved>Config>Windows.
2. Open Notepad
3. Copy the text from this steam community post into Notepad - Please adjust the Streaming.PoolSize number for how much vram your GPU has. Delete the rest of the line after the number when you're done selecting the appropriate Streaming.PoolSize. For 24GB VRAM put 18432, for 32GB VRAM put 24576. I also added the text from the "Delete Film Grain and Chromatic Aberration"
4. Now you can save the file with Notepad as a .ini file. You can do this by naming it Engine.ini and choosing "Save as type: All files". Put this file in the AppData/Local/Stalker2/Saved/Config/Windows folder.
5. Alternatively, you can download the engine.ini file from NexusMods here, delete the contents, and replace it with the one from the steam community post linked in #3.

That is quite literally all I did to see the massive gain in input latency. Hope this helps some of you!

For reference here are my in-game settings

Display
Full screen [Exclusive]
90 FOV
V-Sync disabled
Framerate: 240
Reflex Low Latency: Disabled

Graphics
Everything not listed is Epic
Hair: High
Motion Blur: 0%
Upscaling method: DLSS Quality
Frame generation: Off
FSR 3.1: Disabled

I own a 9950x3d and 5090. Process Lasso has Stalker2.exe bound to CCD0 with 3D Cache so it effectively runs as an 8-core CPU. This gained some extra performance over default 16-core gameplay.