What actually happens to electrons in a circuit when work is done at a component?
What actually happens to electrons in a circuit when work is done at a component?
Between when voltage is higher; before the electrons reach the component, and afterwards.

In both cases, the electrons are still there, and are still electrons, and are still moving in much the same way, and have the same sort of density.
Consider a bicycle transmission, with the bicycle chain being the loop of conductor that goes in a closed circuit between generator and load. The links are electrons. The chainwheel provides the energy. The chain does work on the rear sprocket when it moves.
The only difference between the two sides of the chain is the tension, that's what allows its movement to do work.
The only difference between the out wire and the return wire is voltage, an expression of the potential energy per unit charge, that's what allows the flow of current to do work.
And as transistor says in comments, the result is felt at the rear wheel immediately, even though the chain links move slowly. Well, nearly immediately. The transmission occurs at the speed of sound in the chain material, just as the transmission occurs at the speed of light along the wire.