>That's just security by obscurity - finding encrypted files is not that >hard by scanning for high entropy data, at which point your unique password >manager had better be as good as the well known ones.
No, the best protection is not storing the whole information on the same computer. It is not obscurity, it is a physical barrier.
One part of information can stay in the brain (say "add the name of you cat after each stored password"), or on a portable device (a sheet in wallet, a cell phone), and the combination of the distinct pieces of information can follow a simple algorithm easy to remember (all cap letters are actually small, etc.).
But such methods as well as password managers do not hold against keyloggers.