Hello,
Just wanted to add something on size of screen. It's tricky as it's partly a personal preference.
I've seen various guidance, but two of the more useful ones are 1.5 - 1.9x the diagonal screen size, and 1.5 - 6x the horizontal width. I'd say the first is more a guide to get the cinematic picture, the second range more of a maximum and minimum for comfortable viewing. I think the THX guides just seem to recommend too big a screen size for distance.
Obviously you've then got to filter in your personal preference on whether you at the cinema site front, middle, or back, and choosing within the ranges to suit; obviously 6x width will be more a back of cinema experience.
From my own experience for TV a 26" at 3m has been fine, but at about 4m 32" is probably better. For film I've had 93" at about 3m, whihc was fine, but is now better to me at about 4m. You could go a bit smaller, but once I started to get to around 65" via experimentation it was easier to see the whole image at once, but it had lost quite a lot of the cinematic impact. Obviously this is all personal opinion.
I don't think there's a right or wrong, and there's definitely a trade of in spectacle and the ease with which you see all elements of the picture. It has to be immersive and fill your vision, but you don't want to be misssing a lot as it's out of your main view, or having to look around / move your head a lot to see it all.
If you're looking at 65" screens I'd certainly recommend considering a projector, which would be cheaper at the size, and offer flexibility in sizing going forward. You would though maybe need a supplementary TV. Projectors are good now but you'll still struggle in full sunlight with darker material.
Hope this helps a bit