Honestly I am going to say skip 4K and just go to 5K. They are not that much more. I have 2x5K setup and it is great. The main monitor is normal orientation and the other is mounted on the left at a 90 rotation centered on the side of the first. I keep my work on the main and all the documentation, chat, etc. on the vertical one. I hope to be able to ditch the 2 monitor setup next year and go to a single 8K display.