IMAX laser can be the full 1.43:1 ratio or it can be it can be cropped vertically to 1.9:1. You just have to ask the specific theater to find out.
I saw TFA in full 70mm IMAX in Indianapolis and it was glorious.
I saw Rogue One in standard digital IMAX 3-D, but on a full size IMAX screen (not a post-converted “LieMAX” Screen) in Phoenix. I was actually surprised at how good it looked. Far and away the best 3-D presentation I’ve ever seen. It was a surprisingly enjoyable and memorable experience. Though I’ll admit I was glad I had already seen the film twice in 2-D previously, so I was able to really focus on enjoying the 3-D part of the viewing experience.
I saw Dunkirk in Austin, TX on a full size 1.43:1 IMAX Laser (actually the biggest screen in TX) as my first experience seeing IMAX Laser. I was rather surprised that, as far as I could tell, it was every bit as good as 70mm IMAX film. Just beautiful.
And that experience led to me seeing TLJ at that same IMAX laser theater. I’d have loved to see both Dunkirk and The Last Jedi on IMAX film, but the nearest theater for that was 5 hours away. As it was I had to drive two hours just to get to the laser theater.
Based on these experiences (and seeing The Dark Knight, The Dark Knight Rises, and Interstellar all on 70mm IMAX film) I’d definitely say if you have the chance to see a movie on actual IMAX film, do it! It’s amazing! If you’re a serious film nut (like me) it’s worth driving as far as you have to at least once. If you can’t do that, imax laser is actually a very close second. If you decide to see something in 3-D, Imax 3-D (even if it’s just the regular dual 2K IMAX projectors) is the best I’ve seen.