it's not you, the resolution setting is broken since years and the dev didn't care to patch it for some reasons
I already pointed it out a while ago, no response...
By changing resolutions and fullscreen mode i have finally found the problem source (in my case) - windows app scaling:
I opend the game in 1600*900 in windowed mode and it was almost full screen size (where it shuld be a little bit more than half (of each demention) of 2k momitor)
When i changed to (borderless) fullscreen i checked render resolution (in reshade menu) and it was 1706 * 960.
If we scale this strange res at 1.5 (150% size) then we will get 2560 * 1440 (which is my windows desktop resolution)
And 150% is my windows app size scale param.
Game doesn have a borderless fullscreen mode, and borderless fullscreen in any app always works at windows desktop resolution (2k in my case) despite any changes in the setting. (that's how any app works (from my experiense, i might be wrong), not just this game).
So this game works in 2k/1.5 (in my case).
When i set windows scale size to 100% - game size on 1600 * 900 windowed mode was normal application window size for this resolution. And borderless fulscreen mode is now has 2560 1440 render resolution.
For the experiment porpouse a set windows scale to 200% and game resolution was 1280 720 which settles the theory.
So i gues you have to play at 100% windows scale mode or find a way to set game to true fullscreen mode. (if your prblem source is same as mine).
Sorry for my bad eng - not my primary lang.