I am currently using the windows client of PSO2 but it seems that the resolution is not working correctly. If I used 1440p resolution in window mode, it occupies the whole screen instead of displaying actual 1440 in a 4k monitor. If I play on 1080p it occupies not 1/4 of the screen but scale almost like 1440. Now my issue here is the quality of the textures are not sharp as expected if being rendered on their actual resolution.
Actually I have already a fix on this but that is only on the Steam and Epic version of the game.. I override the scaling of the application, but when I tried that on the Windows version no matter what I override, it stays the same. Hoping they would fix it. I don't play mostly in full screen as my GPU is not made for 4k gaming. I mostly use my monitor for work lol!