1440p vs 4k monitor ps5

Hey, I just got a ps5 and am looking to upgrade my monitor. I currently have an old 1080p 24” monitor but want something that looks better.

I am not sure if 1440p or 4k is better for ps5, I have seen some older posts that say the 1440p is just 4k output downscaled to 1440p, but I see the option to output to it in the ps5 settings (though I can’t select it because of the 1080 monitor)?

I’m looking for monitor suggestions for either

I sit about 75cm away from the monitor currently. Main games I play online are things like Apex Legends and Rainbow 6 Siege. Single player games are ones like Horizon, Witcher 3, Elden Ring.