3. Perhaps the most controversial part. I will write my 24 word seed phrase with "archival" permanent invisible ink in a book. I will duplicate this in another book and keep the second book in a safety deposit box or in a P.O. Box at the post office. (I will check from time-to-time the longevity of the ink.)
It's good solution
IF you're absolutely sure only you who know about this information, even though it's highly unlikely that someone who know you in real life also know you're using method and have power/connection to access deposit/P.O box.
I have doubt about P.O. box to secure important information though.