I have been rather happy with 2k at 27inch, although at times I do feel I could probably use one with higher resolution. Do you find that when you go to 32 or 34 you need at least 4k?
I definitely prefer 27inch or larger with at least 2k, given that I typically split left and right. I wonder if that would work even better with 32/34 at 4k? Also any recommendation on one that works well with Mac?
I personally think the minimum for 27” is 4K and for 32” that would mean 5K. However, 32” 5K doesn’t yet exist yet (although it has been announced), so I got a 32” 6K.*
However, clearly your pixel density requirements are less stringent than mine. What do you mean by "2K"? If you mean 2560x1440, then that is 109 ppi, which is the standard Apple used way back in 2009 for the 27" iMac. If you are OK with that, I suspect it's because you're using it at its intended native resolution. There is nothing comparable at the 32" size. The equivalent pixel density would be something like 3008x1692 31.6". When you go to 32" 4K, I think the text quality is poor at 138 ppi (at my normal seating distance of 22").
Why is 138 ppi worse than 109 ppi? Because at 109 ppi you will use the native resolution. At 138 ppi you have to use a non-integer scaled resolution, which will reduce text quality.
Much preferred is 2X integer scaling at 218 ppi, which unfortunately for an Apple display means the Pro Display XDR.

The Pro Display XDR is 3008x1692 x 2X = 6016x3384.
*I'm personally using the 31.5" LG UltraFine 6K which is 6144x3456 at 224 ppi, so with 2X scaling that's equivalent text size to a 3072x1728 monitor.
I would suggest checking out 4K 32" screens in person to see if the text quality is good enough for you. It certainly wasn't for me.
My office desk has two 24" monitors and it's more than enough space (I can add in my laptop's built in screen if I need even more). I have two 27" monitors in my home office and it almost gets to be too much room and i find myself leaving entire sections of the screen unused
I used to run a 27" 5K iMac (218 ppi) with a 27" 2.5K iMac (109 ppi) as a second monitor beside it (using Target Display Mode). I sometimes actually kinda disliked this setup. I didn't like having the centre of my viewing area being bezel, and it was kind of an awkward use of desk space. Plus I didn't need all that screen space. I'm now on an M4 Mac mini with a single 31.5" 6K monitor, and I like that setup much. much better. My monitor is 224 ppi, which makes for kinda small text, but I compensate for that in Safari by using its zoom setting at 115%.