What you have is fine for short-term recovery - but I'd make sure you have a long-term and/or cold-storage option set up. It doesn't need to be anything particularly fancy: I'd get a rugged+ portable+external single-drive USB enclosure with a single 16TB drive and have the Synology do a backup of your most critical data onto that drive and store it in your bank's safety deposit box or better yet: leave it with a trusted friend who lives in rural Minnesota or similar.
It goes without saying to encrypt that drive as you won't have full custody of it: but use a simple, proven encryption scheme with a large ecosystem that you know that you'll be able to decrypt in 10-20 years' time.
For backup drives that I keep local to me, I refuse to encrypt them because (in my experience) the possibility of being unable to decrypt data in a desperate or urgent situation just makes me wince.