Sell LG 27UK650 monitor to buy LG TV 43UJ634V

TVs require an HDMI 2.0 video card to work with 4k so you will need the PC to have that. Otherwise you will be limited to 1080p.
In the past when I've used a TV as a monitor I found it really annoying if the TV would overscan the desktop losing content at the edges of the screen. I would suggest you check the owners manual of the TVs to make sure that there is a mode that lets you turn that off. It may be called 1:1 or some other name.