Unfortunately, as said above, when you play the game in 'Windowed Fullscreen', you can only play in your native resolution, so if you have the screen size of 3840x1260, you will have to play in that resolution, unless you, as said above, change the resolution in windows itself and then run it in windowed fullscreen. Also it's not hard to do, just Right Click on your desktop then hit 'Display Settings' won't take you more than 30 seconds, I know it sucks but that's not the game's fault it's just one of the drawbacks to Windowed mode. Another thing you could try is increasing the scaling on the Display settings tab? But that would effect the whole of windows. But yeah, that's what happens in Windowed Fullscreen, which makes sense seen it's obviously going to set it to your native resolution. Other option, play in Fullscreen but I know issues occur in this game in Fullscreen, however, that's the only other alternative. 🙂