I am coming from Premiere Elements 11 which had a device choice titled "Mobile Phones and Players" and presets under that for Apple iPhone...etc. These presets produced appropriately small files for use on an iPhone. They are missing in Ver. 14. The smallest preset available for a mobile device is 1280x720 and produces huge files for an iPhone. Can you share the settings of any custom preset you've created that produces a file size in the neighborhoof 9000 kb per minute?
1280x720 are not at all too large for an iPhone. In fact, that's kind of the ideal size for a mobile device.
As I show you in my book on Amazon, you output video for a phone or mobile device using Export & Share/Devices/Mobile Device with the HD 1080 or HD 720 resolution. This will produce an optimized MP4.