I would:
On macOS:
- Quit Obsidian
- make backups
- drag (or copy) your vault folder out of iCloud Drive and put it somewhere that isn’t already being synced
- Open Obsidian
- Open the Vault Picker
- Open the old vault in its new location
- enable the sync plugin
- go to Settings → Sync
- Enter your credentials/set up sync, and enable the sync features you’d like to use.
On iOS devices:
- Open Obsidian
- Open the vault picker
- Create a new empty vault with the same name of your moved vault
- Enable the sync plugin, log in, and choose the synced vault