I got a Plex server without enough horsepower for transcoding. Therefore I wanted to transcode my video files to a format which doesn’t need transcoding on an iOS 18 device. In what should I transcode? 1080p MP4 with H.264 and AAC sound?
I think this will depend on both the iOS version (which you already shared) and iPhone / iPad model.
If you’re using Handbrake to transcode your videos, they have a bunch of presets to ensure compatibility.