Are there any good reasons to NOT symlink 'System Folders' like Photos or Music? I am currently adopting oDrive for all my cloud storage needs. The only restriction that oDrive has it that it creates a folder called 'ODRIVE' on your computer. Everything that you want to sync has to go in that folder. I have now symlinked my Creative Cloud folder (for adobe CC) but I would REALLY like to symlink my Movies, Music, Documents, etc. That way oDrive manages my backup process, I continue using my usual workflow of saving photos to Photos and music to Music.

But I'm uncertain of how the Apple OS treats those folders. As I believe they are "System Folders" and have requirements on them.

So is there any good reason to NOT symlink 'System Folders?'
This is fine! Go ahead!

Symlinks or hard links are followed by the system, so you're free to create them within any of those folders, or indeed the folder itself.