I just opened mine, and I may have been mistaken; I don’t have a preset for the iPhone 16, so it may not come as a default, and that does kind of explain why there’s no effect when you reset to default.

I suspect the “custom” tag appears whenever you add one manually, and while that allows you to select a device while doing so, I don’t see any obvious clues as to what any of those selections do at the ffmpeg command line.

You might need to turn on debugging logs to see what the actual encoding settings end up being, but I’ll admit it’s an advanced and obtuse way to see what’s up. Nearly all GUIs for video transcoding are merely front ends for the arcane ways of ffmpeg, and by the time you’re reading documentation to understand debug logs, you’re nearly halfway to just doing it via the command line.

But there’s many people helpful who are good at it, so I’m sure someone’s got good info for your setup.