If you are worried about that, you have to be really careful with OPSEC.
The "look over your shoulder" attack is omni-present. (Also easier to prevent with paper, in general, than with a larger computer screen.)
A simple safe will stop most prying people. And if you die... Well, you are dead... there ain't much stopping anyone at that point.
Keeping secrets is hard. Very hard. There's a reason for the most part... I don't bother, except if/when I need to, and even then, if they can be timed out, all the better.
Paper also has a big benefit in that we know how to destroy it. :)
... Simple things are often best. Understanding how your system will bend/break is critical in security situations.
Not OP, but you seem to be thinking about this in a particular way. There are some things I don't want to be read, but not in the sense that they're "high value" in a way that would attract motivated attackers. I'm not worried that my friends and family are going to shoulder surf, trick me, hack my devices, or threaten me with a big wrench to get at my private thoughts.
For these purposes, written journals or letters can be opened opportunistically if found. If I had a safe, it would be opened after my death. If the documents are known to exist in the clear anywhere, then they're subject to probate.
But if they're encrypted and the secret is unknown and hard to guess, then most likely everyone gives up and that's the end of that.
Also: If your papers are taken, you probably can figure it out.
At the nation state level... honestly, they'll read it straight off your montior's emissions. TEMPEST exists for a reason.
For these reasons, I tend to NOT trust my computer for absolutely critical things. I prefer paper.
Also remember yesterday's unbreakable crypto is 10 year's from now's breakable and 20 years from now they'll be doing class projects on it in college.