As regards understandability and minimising "magic boxes", this means it's pretty much just core OpenBSD (kernel & base system). The moment you add the usual desktop environments or a huge monolith like Firefox, you've lost these benefits. Same with drivers. More drivers you have, more the system becomes byzantine. Keeping things minimal and well designed yet useful must be a continuing challenge for OpenBSD!
Hah. Going by the "anything you compile with a magic box becomes itself a magic box" argument, even the OpenBSD base is a magic box as soon as you run it on an x86 machine.