Well, by 'TV,' i'm thinking... 32" and up, So..
the graphics-quality of the games is definitely not going to look its best. The optimal (best-looking, best-feel) is min. 1080p
I prefer up-ing Resolution more than anything (i.e. Quality)
That being said, 1366x768 is an OK-resolution and should do your gaming-PC justice.
And, 4K is sort-of overkill unless you have a 55" 4K TV that is at most 3.5ft away from.
Hope this helps.