Yeah you can be lucky or you can be unlucky, for giggles you could start AI War 1 or a game that has 4:3, on my new screen I noticed that I can't even see text inside the small windows (too small), and full-screening dosbox.. yikes , then you can read stuff, but you better enjoy black bars.... and 4x larger pixels although it still looks pretty good with no filtering ;/
Such fancy screens, not just wide-AR, are always gonna hit one or two issues you never thought about. For older games (Specifically older Anno games come to mind) it's not AR support, it's the size of the GUI elements (they scale down the wider the AR is.... ) in Anno 2050 for example, the build menu occupies around 3% of the screen, really iffy to use that. And the money indicator is at the top left, but you only see what an item costs at the mouse pointer build location. So yeah, ups and downs ;/ I debated for a while whether ot get wide-ar or normal AR, and my laziness in not wanting to move my head resulted in a "standard" 16:9 (2560x1440@144hz though) and speaking of HZ, japanese console ports handle non-standard AR and refresh usually extremely badly.
Oh well, enjoy your screen
Hopefully it will last you many a year.