Im shooting a short this month with an iPhone and a 1DX. I’m sure it will cut together well (lol, Im not gona cut them together)
I originally had experience shooting on the iPhone back when I worked on the series ‘Laps’ - which had the entire first season filmed on the iPhone 4 I believe (this was back in 2011). I also DP’d a short about a year ago where we filmed a sequence on an iPhone 6s+.
You can get great footage from a phone. I’m also putting together a video on how I use it (part of a ‘how-to’ production themed series). The gist of it is I make sure I have good lighting (obvious), keep an eye on battery and storage and pair it with the right accessories depending on your situation. I’ve used MoviePro (app), a Moment lens set, and I just picked up a Smooth Q for steady shots.