I have a 4k Sony 55" in my living room and it is a great picture and I am happy with the purchase. I have watched some 4k content on it and it is absolutely stunning how sharp everything is. I also have a 150" projector in a game room area which runs at 720p.
The game room with the projector is a converted garage with only a window A/C unit and space heater while the living room has a more comfortable couch and is much cooler in the summer and warmer in the winter.
The 4k TV is a better picture in every single way, but if my sports team is playing you will find me sitting on the less comfortable couch in a less comfortable room watching a vastly inferior picture for one very important reason, size matters.
Please don't misunderstand me, an OLED TV is absolutely stunning and if it is within your budget to do so, go for one. However, I think 4k has become common enough on TVs that the price has gone down considerably, but there is a still a premium placed on the OLED displays so you typically have to give up size in order to get an OLED on a budget. And in my opinion 49" is better than 42", but 55" is better than "49, and 65" is better than 55" etc.
As far as the specific options you mentioned, I have a friend who has a 55" TCL very similar to my Sony and his picture quality is not as good as mine. I haven't seen anything from LG recently that wasn't a OLED or a computer monitor so I can't comment on those, but both Sony and Samsung will definitely be a better picture than the TCL assuming the price is similar. I have personally noticed that is especially true with sports or fast action movies as the refresh rates are better on the Sony particularly.
