iCloud or any other reliable cloud service (OneDrive, Dropbox, or, should you be so inclined, your own personal NextCloud server) is the only reliable way to go in my opinion and experience. I keep an iMac and MacBook in sync and use iCloud for Documents, Desktop, Photos, and my music library; Dropbox for business-related documents and collaborations with colleagues, clients, my accountant, etc; and OneDrive as additional iPhone photo backup and collaborations with colleagues and clients who don't use Dropbox but Office 365 with Sharepoint/OneDrive instead.