There's an age old debate about oled and qled. Generalising massively but oled is the best outright picture especially with contrast and black colour tones, but some suffer screen burn where the sky sports logo will seem to etch the picture. Qled won't do this but the trade off is the picture isn't quite so good with dark images.
4k is pretty standard these days at that price, and most come with seemingly infinite adjustment.
Check out hdtvtest on YouTube, he's very dry and knows everything.
All flat TVs will have crap sound so I'd ignore them in that regard and get a sound bar or connect to your hifi system.