So would you say getting a 27" 4k monitor be worth it or would 32" + be something better for 4k?As a person who owns a 27" 4k monitor and something close to 1440p pixel density, yes you can notice the difference. This is mostly with text. It isn't much and there are a lot of tradeoffs that come with a 4k display.
Honestly, if I had a system that can display 4k on the highest settings at 120 fps with HDR. I would go with a 4k display even at 27" or smaller. The issue is can my system handle that? I think getting a better overall picture comes before getting more pixel density. The human eye can perceive up to an 8k display on a 27" monitor from the typical seating position.
There are some slight advantages to more pixels. You can turn off AA.