At only 50" you are only just able to resolve 4k at 3 feet. 8k would be pointless for a screen that small unless you're 1 foot away!
I dunno, I can see the pixels making up text in Windows. Not really noticeable when gaming as I sit a bit further back but aliasing is still janky at 4K and text could be even crisper. Like iPhone crisp. I like the way the image on an iPhone looks like it's painted on to the screen, I want to experience the same thing on a TV. Maybe I need OLED TV instead. Or 8K! I think a 5K iMac at 27" is pretty close to that feeling.