I find it hilarious that so many people are obsessed with "4K gaming", to the point all the review sites now include 4K resolution in their graphics card tests, yet in reality it makes so little difference.
With a typical 27" monitor at normal viewing distances, gaming at 4K would just make things a little bit sharper. You might notice it to start with but, once you're immersed in the game itself, you'll never notice the difference. In exchange for this marginal benefit, you'll get massively reduced performance compared to 1440p.
Contrast with a ultrawide monitor, which provides massively more immersion due to the wider aspect. Once you've experienced it, you'll never go back. It's also easier on your hardware as even a 34" ultrawide has only 60% of the pixels to shift as does a 4K display.