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TV's are a bit of a lottery to use on a computer. Many have considerable lag from input to display, not a problem watching TV but it could be a big problem for use as a computer if you're typing, moving a mouse, or gaming.
Depends how recent the TV is. Some have a "game mode" that minimises the processing (and therefore the lag) between input and display.
Anything that has 100ms of lag or more is quite unusable, especially long term. It's the reason why a 42" monitor is quite a bit more than the a 42" TV.
https://thenextweb.com/plugged/2017/10/01/use-4k-tv-pc-monitor/ links to some useful info about which TVs are ok in terms of lag.
A bit small.
Current plan is one similar to this (which is why I need more than 50cm depth to a desk):
https://www.overclockers.co.uk/acer-dm431k-43-ips-3840x2160-4k-60hz-5ms-widescreen-led-backlit-gaming-monitor-black-mo-14r-ac.html