What is the difference in performance between variable pitch prop and two fixed propellers for take-off and cruise speeds?
This doesn't specifically answer the question in the title, but from the body of your question I would say it's possible, if you had an electric push/pull configuration with a motor in the nose and one in the tail, or at the back of a fuselage pod with booms like a Cessna Skymaster.  

The aft facing motor could use simple fixed pitch folding propeller that folds aft and trails in the slipstream when not being driven (popular with motor gliders) and it would be used only for take off and climb, with climb-optimized pitch.  In cruise that motor could be shut off and its batteries assigned to the front motor and its blades would fold into a near zero drag trail position.  The front motor could have a fixed pitch prop optimized for cruise.

The key issue would still be worst-case climb performance.  It would have to be able to make enough thrust on the single cruise pitched prop at the front to climb decently if the back motor failed.  Possibly if the front electric motor had some sort of emergency boost feature, where it's torque could be temporarily increased (enough to get its coarse pitched propeller up to red line) for a certain number of minutes without overheating, would be sufficient for single engine safety, with the rear propeller folding back on its own for you.

For single engine performance on the rear motor, you might get away with just a brake for the front propeller to stop it from windmilling if its motor failed.  Not as good as feathering, but far less drag than windmilling.