I can tell of my experiences.
In the past two years I have experimented with a fair amount of monitor sizes and resolutions. I am a 3d animator and so screen real estate is very important for me thus the higher the resolution the better so I went for 4k obviously and here are my outcomes.
The first 4k screen that I used was a Samsung 28" and although the pixel density is great its rubbish to work on. A colleague of mine got given the same monitor as me and after around two months of working on that monitor we were getting headaches and migraines and serious eye fatigue. The monitor is too small to accommodate that resolution (Don't get me wrong, games look very crisp on this thing but you don't play games 24/7 you actually use your pc for allot of other things and most of it includes staring at text or a UI).
After using that 28" samsung 4k monitor I must say I loved the screen real estate I had with programs like Maya and zbrush and after effects, substance painter etc so I wasn't going to drop the 4k situation, The goal was to find a larger monitor so I went and took my pc to Game and tested some 4k TV's out and I have found that the sweet spot for 4k gaming and working seems to be 49" and 50" it gives me the perfect size, It's like using two monitors with no frame separating them while keeping a pixel density small enough that you don't see pixels. I can work in Maya and have photoshop open next to each other and play a movie above them and it all fits beautifully and the size is perfectly workable.
At the new place that I am currently working I am using a Philips 43" 4k monitor and its great! The pixel density is so tiny you could call it a retina display and that's great, but when I go home and work on my 4k TV I feel like I have a better experience in the fact that I don't have to work full screen in Maya, as I said earlier I could have Maya and photoshop open next to each other because the screen is big enough to make the comfort of reading everything perfect. Although they are the same resolution the size of the screen plays a huge role.
I now recently bought myself a 55" curved Samsung 4k TV with HDR capabilities and that is just another level of PC gaming altogether that I am not going to go into right now. The immersive feeling I get when working is amazing although those extra 5" make the rows of pixels visible. It's not hugely visible, most people wouldn't even notice it until I point it out to them and its only on certain types of content with very flat colours that you can sort of see it so if its pixel density your going for I would stick to the 49" to 50" as I feel its the absolute sweet spot for 4k displays.
The Philips that I use at work is really good value for money though as it has 2x Display port as well as 2x HDMI and one VGA input as its an actual monitor not a TV. It is also a proper 10 bit Panel however don't think that your going to be able to play an HDR game on it. 10 bit doesn't mean HDR capable as I found out the hard way recently which is why I decided to stick with the HDR Samsung TV. But as a monitor for work it is perfect.
If you are going to use a TV like the one's I have described then don't think that you can put it on its stand on your desk and work or play like that, you won't enjoy it as you will be looking up all the time and will probably get a stiff neck lol. I would suggest mounting it on your wall as you can sit a bit further back from it and get a bit more central to it with regards to height, This also gives you the option to raise or lower the screen on the wall mount and swivel it.
Here are some pics of my setup with the new 55" Curved TV. The funky bumpy stuff on the chrome bezel at the bottom of the screen is the protective sticker that I hadn't pulled off yet.
View attachment 64924
View attachment 64925
Hopefully this sheds some light on the subject for you.
