- Edited
Agreed - OBSD has always been the model! (I was playing off of an earlier comment :-) )
At my time, OBSD was (is?) the security standard - but was server-oriented and lacked a lot of the applications I wanted. I ended up using https://wiki.gentoo.org/wiki/Hardened_Gentoo which I liked a lot and was very much influenced by OBSD, but required a big honking machine.
Qubes running hardened Gentoo would be the way I'd go if I had the hardware and the energy; now I run Qubes with a straight forward fedora linux dist. and flush virtual machines regularly and frequently.
GOS is hardened and minimal (as was OBSD) - but has applications (as does Hardened Gentoo), and offers a LOT to a careful user.