SANCTUM
In your vault — a folder you picked when you set up Sanctum, full of plain Markdown files you can open with anything. See where it is anytime in Settings → Library. Sanctum never hosts your notes; there are no accounts and no Sanctum cloud.
Yes. Place your vault folder inside iCloud Drive, Dropbox, or Google Drive, then open that same folder from Sanctum on your other Mac — your cloud provider handles the syncing. Let syncing finish before switching machines, and avoid editing the same vault on two Macs at the exact same time.
Yes — Settings → Import brings in Obsidian vaults and Notion exports (or any folder of Markdown). Imports only ever add; nothing of yours is merged or overwritten.
Settings → Backup exports a complete copy of your vault, images included, whenever you like. Your vault folder is also just files — any backup tool that covers that folder covers Sanctum.
Open Library → Recently Deleted — deleted pages are recoverable from the vault's trash until you delete them forever.
Ember, Sanctum's AI layer, is optional and off by default. Add your own API key in Settings → AI to enable it; your prompts go directly to your chosen provider, and without a key everything else works exactly the same.