The technology is so easily reproduced, I avoid the big name brands these days. Many of the cheaper brands offer similar, if not better, quality and reliability, for a fraction of the price. I've had especially good luck with Insignia products from Best Buy.
As far as specific technologies, I haven't really researched them in a few years, but from what I last remember, OLED looked like a nice advancement in tech. Outside of that, 4k was still pretty useless due to extremely limited content in 4k. Maybe that has changed some in 4 years, but not sure. Certainly wouldn't go 8k yet unless you are just a top notch innovator/early adopter type that must have it and is willing to seek out the content yourself.
As for quality and how big the tv should be - most people overestimate. They sit in a store, 2 feet from the TV and see the difference between 4k and 1080p or 720p. In reality, no one sits 2 feet from 72" televisions. The best thing to do is measure how far you or your company will be sitting from the TV, then use a chart:
Display Size, Resolution, and Ideal Viewing Distance