From the Discord 
bot, but the official stance →
iCloud on Windows is known to cause file duplication and corruption issues. We highly suggest avoiding using this combination.
Courtesy of @Synchronicity →
These are the methods currently believed to work for syncing between Windows and iOS devices:
• Obsidian Sync
• Self-hosted LiveSync plugin
• Remotely Save plugin and various cloud services, including Amazon S3 or S3-compatible, Dropbox, OneDrive for personal, and Webdav
• Git with the Working Copy or a-Shell iOS app
Big thread on the different options →
Obsidian Sync has an education discount, so that’s also something to consider →