I think every piston plane has a single point of electrical failure, for a total loss of everything - in the form of the master switch.
Certainly most SE ones have such a POF.
On the 'homebuilt' ones nobody worries because you are supposed to be VFR
but for any serious touring I would have a backup horizon, and a backup GPS and radio. This is what I have in the TB20, and would have in anything else.
One needs either a second alternator which feeds the backup instruments, or a battery for them, with diodes so that the backup avionics can draw power from either the main bus(es) or the backup bus.