thank you all.

ill take the advice and get a real monitor instead of tv.

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well, i saw a 299€ 43" 4k tv at gigantti.fi , without thinking it much i just bought it.
its not bad, it is nice to have so much room in ur monitor, next thing i need is new graphics card.
its has some smart features but i don't trust it so much that i would connect it to internet.

(settings menu mentions linux kernel and ssleay) so at least it doesn't run windows :P

I really don't know how people use such huge screens - I used to use 15"/17" TFT - but just found them to be too big for me.

I now use a 10" & two 11.6" laptops & an 11.6" desktop monitor, & find them quite big enough.

I've just ordered an 8" TFT as a back up monitor, & I'm sure it will be fine too.

Mind you, I did start out using a 9" CRT with my first computer, an 8088 XT - maybe that has something to do with my preferences.

I use a 1080p TV as a monitor. I sit at a regular distance, set my font DPI to 160, and use a wireless keyboard and trackpad. It's comfy, but it's not optimal for actual work because you can't fit as much information on the screen (the fonts are big).

I'd imagine that with 4k, you'd set the DPI to 320 or 384.

A friend recently purchased a 42", 4K monitor for use on his mixing desk to replace 2 24", 1080 monitors. He, effectively, gets the equivalent of 4 of the old monitors (there's a bit of resolution to spare, of course) and doesn't have to mess with xinerama and the like. It is a bit odd trying to use a terminal on one but, if it were left to me (I keep telling him to use the terminal more, on any case) I'd just set up the term with the appripriate font size and it would be fine as a window.
He currently uses fluxbox but I've mentioned, and will keep doing so, ratpoison because some kind of tiling on that kind of display could be awesome.
Personally, I've a (recently purchased) 27", 1440 monitor and a 24", 1920*1200 monitor and, while I like the setup, I think I may be changing it for one, large, 4K display in the next couple of years if and when I upgrade my desktop.
I have to admit to using my system as my main "TV" and movie watching setup but, even so, I like having the real estate to multi-task without having to cover things up.

I've found two 720 (32" & 40") and two 1080 (both 32") TVs perfectly adequate for work with PCs with digital outputs, with either PC HDMI ouputs, DVI to HDMI adapters, or DP to HDMI adapters. For connections to a TV VGA port, quirks made use less than optimal but nevertheless usable. Since I only use PCs for work, I have no experience for games.

I bought a 4k 42.5" LG "display" with 4 HDMI and 1 DP input plus remote control that in most regards worked nicely, but for several reasons I returned it, including its remote control uses Vizio codes that interfere with its use in the same room as my Vizio TV. Even though the LG remote was IR, it could be pointed in nearly any direction and still operate both the Vizio and the LG. I bought it for several reasons, of which a major one was POP/PIP with up to four inputs onscreen at once. But for the remote interference I probably would have kept it. The Vizio can't go because there's no way to replace its PIP/POP and 8 inputs functionality.

In every case I was or am using FOSS gfx drivers only, mostly with Intel gfx, a very few with at least 5 year old ATI and NVidia.

I did find the techspot.com URL in post #5 enlightening.

yea, i had (or my father had) a 286 with crt monitor maybe 9-10" :P

i don't know how to set DPI. but i did set at "Universal Access" -> "Large Text" and "Cursor Size" -> Large.
and i set window scaling to 125% at my virtualbox windows 10 pro guest, which runs couple of games.

yes, that's why i am happy with this setup. my puter is my TV setup like yours. and if i code i can have several programs/editors open and it is nice.

that's why i have to buy gfx card next, my "gtx960 gaming" is obviously way underpowered to use with 4k monitor. nvidia 1060 is going to be my next gfx card.