When I was in Colorado I was by myself for the summer while my daughter was at home. So, I went to places like Best Buy, Wal-Mart, etc and hung out in the electronics section. I would gently make a comment about TV cost or such to spark a discussion. If the person said something like "why the heck is this 65" TV less than the 55" TV?" I would explain the technical specifications to them as to why and whether they needed to pay the extra or not. It was a lot of fun. Quite often I got asked if I worked there and when I would say no, they'd reply "well dammit you should" lol. One couple even pulled someone from Best Buy and said you should hire this man, he knows his stuff better than any of you here. I kinda felt bad for the kid.
Anyhow, I haven't answered any of the questions posed. And that is because it is all subjective. If quality is not a huge concern, by all means roll with a 65" 60 Hz refresh rate TV with a low contrast ratio. If you want a good Smart TV experience, I suggest never buying a TV because of the applications it has and purchasing a Roku instead. Then you will have a consistent "Smart TV" experience on any TV you own.
If I were to buy a TV right now, I would probably lean towards a 120 Hz (true accurate spec) refresh rate with a good contrast ratio (e.g. 1,000,000:1) so you have dark blacks and I would probably go towards some 4k OLED over LCD and Plasma. I've always had good luck with Vizio, however, my last TV purchase was a Samsung. So far over the last year it has not disappointed me.
I know nothing about sound bars because I built a home theater system.
What inputs/outputs a TV should have is subjective to the owner. If you are going to use multiple peripherals such as gaming systems, blu-ray players, cable box, etc .. you will want numerous HDMI inputs. Let's say you don't want cable or satellite, then you will want to make sure the TV has a built-in TV tuner so you can connect your over the air antenna into it and scan for local channels.
For gaming I would definitely want OLED.
That's about all I can toss out right now.