Can I read my linked notes offline, with my Supernote switched off?

Yes — any note the app has already fetched once is kept locally, so it opens instantly even with no Wi-Fi and the device off. Getting a note for the first time, or pulling a newer version, normally uses the device — but if it isn't reachable, the app can offer the note's last-synced copy from the Supernote cloud instead (it may be behind your latest ink). When fully offline, the app stays quiet about updates and just shows your saved copy.