What you get will be personal be it OLED or led. It could be a serious amount of money for you.
Try to look at many. Try to take a data stick with a 4k clip on it, use it as a reference, hopefully the one that you would want has a USB 3 input. Try to see HDR content at least. It is good.
Check the set up scales well. Cannot help in the US but U.K. we have 1080i over the aerial to compare. SD, that will never look good.
Go look through avs forums etc. Someone will have the set you fancy and there may well be a dedicated forum to the set model number.
Check that the set has 4k on all hdmi inputs, some do not. Try to compare them side by side, not always possible.
Then, don't listen to anyone here or on any forums. Listen to your eyes.
You are the one that will have to shell out a lot of loot and have to live with the decision. 4k done well on a good set is sublime. Bluray films are superb. Streaming is good, if the provider does a good job but not as good as bluray. I hope to see what Apple TV can do soon.
However, for streaming, I have a reasonably fast connection and no data caps. I don't have any home servers so cannot comment on that.