I agree with you and have a Sony 55” as my main visual media. It’s in a room along with an amp/receiver, a center speaker, and a pair of studio speakers. I sit about 10’ from the tv and 8-9 feet from the speakers. It is not a completely immersive experience but I didn’t I intend it to be. It is however, a very pleasant place to watch tv as the world go by.
The tv is a 4k with a 4k dvd player with is also a Sony. The player up scales to 4k anything it plays and it does help a bit.
My music room is smaller and includes an old 40” Samsung and lots of old audio equipment along with book shelves cabinets, and a cd cabinet. That also happens to be my workout room as it is partially underground and sonically has less reflections.
I don’t know if anything I have said will help except the tv size debate your going through but after you make your choice, you will get used to whatever size it is and regrets will fade. Even if you get an 80” inevitably there will be compromises about size and placement so do your best guess and live with it.