FYI, absolutely nothing streams in 4:4:4, and once any HDR content starts streaming with these settings it will switch away from that anyways.

These are good settings to use, but they don’t magically increase the quality of the stream.

I think it really depends on your gear/equipment and your own eyes/ears. Every setup is different (not just in screen and speaker quality but also in internet speeds and streaming apps). Likewise every person is different in what they’re used (what their quality standard is) to and what they notice.

Streaming 4K can range from awful to very good. 4K Blu-ray will look and sound leagues better than awful streaming but might look nearly indistinguishable and only sound slightly better compared to very good streaming and not overly picky eyes/ears.

The best is to test for yourself. I’d say if you’re unsatisfied with the quality you currently have it’s worth exploring, but if you’re already really content with the quality you currently have then maybe it’s not worth the extra cost?

The iPhone doesn’t have an adjustable aperture. There is no change to the amount of light being let in.

I don’t think this is possible, as there are many instances where a 4K upgrade releases as a different listing (often because licensing changes hands between distributors). I don’t think there’s anything in the iTunes database that links together different releases of the same movie, and it can’t just go by name as there are often many films with the same name.

Unfortunately I think you just have to do a manual search each time you go to watch a film to see if there’s a better version available. Or you can keep an eye on CheapCharts, but again that might not catch new releases under a different distributor, I think the “Upgraded to 4K” section only tracks titles that have upgraded to 4K under the same ID that was initially an HD only listing.

Huh? OP is saying they’re willing to pay more, they just want some sort of indication or notification that a film is available in a better format that they can upgrade to.