The IMAX version is 1.90:1 in theaters of that height or greater - some IMAX locations are more like 2.00:1 or 2.20:1 and it’ll be that ratio in those locations. No 1.43:1 sequences.
Outside of IMAX, the ratio is different. All 2D showings are meant to be 2.40:1. All non-IMAX showings in 3D...
I hope this doesn’t sound trite, but: the proper black level is the one that the specific master being viewed was timed for.
By that I mean: in ye olden days, you’d make one version of the film, approve one answer print for all others to be measured against, and everything else was an attempt...