If you want the best version of Oppenheimer, you are going to want the 4k Blu-ray.
Lossless audio is better than what steaming can provide, even vs Atmos (which this doesn’t have).
The other main factor for this movie in particular is the aspect ratios. Streaming only provides one aspect ratio, while this Blueray will switch aspect ratios to be more in line with the IMax filmed scenes.
I’m not here to shit on streaming vs 4k Blu-ray in general (which many will do), but Christopher Nolan movies are purposefully made better on the disc beyond the normal comparison would be.
Edit: this is assuming you have a good home theater setup to take advantage of what physical media offers
Make sure you aren’t buying the really old Apple HD instead of the 4k.