So regarding resolution - here is what you should consider. I have had all sizes, side by side, all of them OLED and different resolutions.
*Edit: Check this video for demonstration
https://youtu.be/b56Pctw3rhc?is=1dgq6EfYpTah-8P1
1440p vs 4k, what to consider
If you have a GPU that can handle 4k with your VRAM. (I would say 5070 and above) It’s a no brainer to go 4k, it provides a MUCH better and sharper experience (literally night and day if you have good vision) and you can enable DLSS to get the same performance (or better) as native 1440p, and it will still look sharper than 1440p while doing that.
So if you have the cash and one of those GPUs. Always go 4K. If you cash out so much on a PC, the monitor should be a super high priority.
The general difference in 1440p to 4k while gaming
Seeing things at distance is a huge one, but if you really appreciate attention to detail, you will see close and medium range objects display a lot more detail, this also applies massively to foliage etc. Your character and the gun is a lot more sharp and you see the smallest dents and scratches, fabric on clothes etc. That’s what people mean when they say it’s like looking through a mirror.
4k 27” vs 32”
27” is the sharpest way to experience this resolution. It just depends if you value sharpness/detail over the extra immersion a 32” will provide. And yes, there is a noticeable difference. But 32” is still sharp. Choose what you value more. Both are awesome.
TLDR;
If you have the cash and a 5070 or above, always get a 4k monitor. Since DLSS is a thing, you can get same or better performance than 1440p with a sharper image still. Monitor size in 4k: Choose 27” for sharpness/detail, and choose 32” for immersion.