It should be immediately obvious if you open the Steam overlay. The text will lose its clarity and appear fuzzy/blurry depending on your native resolution. If you still don't see a problem then I guess you're one of the very few outliers that don't have that problem or somehow have the game consistently running in borderless fullscreen (without the app) without having to mash alt+enter a bunch of times until it randomly works. Or you're blind
But yeah, you should install FAR anyway if you have issues with cutscenes/performance issues/hiccups.