What is an electron?
This is where I'm at:
1. it apparently has some definite-valued properties independently of the measuring apparatus: mass, total spin, total angular momentum, charge, ...
2. it has some properties before observation that are dependent on the measuring apparatus: location, momentum, energy, x-spin, ... amplitudes. These amplitudes are the maximum amount of physical information, from the apparatus' perspective, between the electron and the apparatus.
3. it acquires properties, in the guise of definite values for amplitudes, only upon observation by the apparatus