You can make everything bigger in OSX finder (text, spacing, the sidebar etc) but really depends on how adjustable your third party programs are that you use. 

I run my Samsung UHD TV & Thunderbolt Display both at 2560 x 1440 (retina), as the TV still renders at that at 4K and does not actually put out 1440p, so while I’m at a lower resolution from the computer, the TV stays on 3840×2160 at 60hz if that makes sense. It’s crystal clear (alot better than the oversized 1080p).
But if you wanted to work at 4K for video editing, photoshopping etc, then it definitely works perfectly.