Resolution is one field
720p, 1080p and 4K describe image dimensions or commonly used resolution categories. They do not tell you the bitrate, source condition, colour treatment or subtitle quality. A poster marked HD does not prove a particular video edition is available.
Choose for the screen
A stable lower-resolution stream can be more comfortable on a phone than a repeatedly buffering 4K stream. On a large television, compare the higher-quality option if the service, plan and device support it. HDR is a colour and brightness capability, separate from resolution.
Choose for the speakers
AAC, DD+, stereo, 5.1 and Atmos describe audio formats or arrangements. The useful choice depends on the playback chain. If dialogue disappears while effects remain loud, check your output and try a supported audio track before assuming the film itself is broken.
Check the edition, not a guess
Watch now opens title-specific viewing choices. Read the available quality and language information there. The catalogue does not operate a video player, and a quality guide is not a promise that every listed film has every format.