Syncthing is worth trying for file synchronization.
Good things: Sends updates to changed files directly between your devices, no cloud service needed. Flexible, can connect any directory to any directory. Free.
Bad things: Installation awkward on desktop. No iOS version at all. Simple but confusing user interface. Sometimes devices can't find each other.
Future promise: Open source and peer-to-peer, so will stay decentralized. iOS version more likely in the future, as the language Go gets better support for the operating system.