DLSS does not appear to change the internal rendering resolution in SimRail.
No matter which DLSS mode is selected (Quality / Balanced / Performance), the game always renders at 100% resolution.
I verified this using the in-game debug/overlay information, which always reports full native resolution rendering even when DLSS is enabled.
Steps to Reproduce
Enable DLSS in the graphics settings
Select any DLSS preset (Quality / Balanced / Performance)
Observe the rendering resolution via debug/overlay information
Expected Result
Different DLSS presets should result in different internal rendering resolutions (lower than native for Balanced / Performance).
Actual Result
All DLSS presets render at 100% resolution, with no change in internal resolution.
Additional Information
Tested with the DLSS DLL shipped with the game
Also tested with the latest NVIDIA DLSS DLL
The behavior is identical with both DLSS versions