Is it really a big screen movie?

No camera would mean no images. So, no.

I just got back from seeing in in 70mm. Not as visually impressive as some other Nolan movies like Interstellar or Dunkirk, but I'm very glad I went to see it on the big screen. It would not be as enjoyable at home, imo.

No. I saw nothing amazing in this film when I watched it in IMAX. Not even sure why they bothered. It will play just fine on regular screens, at home, or even a phone. It's more content based than amazeballs visuals.

The home experience just isn't the same unless you have an actual theater in your home, and even then...

The total immersion, the fellow crowd members excitement (if they have proper movie etiquette), the fresh theater popcorn and fountain drinks, the smell of the guys nachos behind you, the newest trailers on the big screen, the mess that someone else has to clean up, the fact that you can't do anything about that thing that might come up at home that would normally distract you, the person next to you laughing or crying while you are laughing or crying too, walking past the rows of posters on the way to your theater, that murmer that starts right when the lights go down after the trailers because the main event is about to start, the heated recling seats with the little table that swings in front of you, the theater wide jump and gasp at those moments that take everyone by surprise, the fact that leaving your home and going to do this simply because you love cinema so much that it becomes an event rather than killing time...these are some of the reasons why I go to the theater.Put aside the superior picture and sound, which it definitely is.We go to the theater to make a movie special.
All of those things are very small individually, but they add up to something extraordinary. I'll admit I'm more inclined to make a point to see a special affects driven movie on the big screen, but any movie at the theater is better. In fact, it can make an average movie good, in certain instances. The Meg is a perfect example. Anyway, I'm seeing this next weekend, so I'll hope it's great.

I'm glad I saw it in a theater - the setting of New Mexico was a big part of the film and the big screen was needed for that. But I don't think it would be much better in imax

All movies are drastically better in a theater. At best you're getting 10% of the full experience of a film when watching at home. For a film shot in 70mm there's almost no point in trying to watch it at home.

The first 2 hours had a decent pace.

Very interesting, the race for the bomb, communism, Los alamos

I needed more nuke footage,

Yes, definitely see it on IMAX. Because of the sound as well.
Always experience a piece of media the way the artist intended.
Think of it this way: once its gone, its gone forever. You'll never be able to see it in a theater once it leaves, you will forever be able to watch it in your home whenever you want.