You have touched on what will be a BIG problem for aircraft accident Emergency Responders. Electric automobiles are already a BIG problem for Emergency Responders, with the Tesla system using around 375 volts and the Porsche Taycan about 800 volts. Dousing a flaming wreck with water and foam is usually the only option for most Fire Fighting organizations and is usually effective on hydrocarbon fuel fires; however, the materials used in the current crop of high energy density (HED) batteries (such as Lithium) are pyrophoric and ignite when exposed to air. Lithium will also react with water, but at a much slower rate than, for example, Sodium metal. The technology of HED batteries is rapidly evolving, and my limited understanding of their chemistry may be outdated, but the electrical hazard is pretty much a given. Isolation switches for an HED battery will confine electrical hazards to the battery pack itself if electrical circuits are undamaged; however, it can be expected that most systems will be damaged or otherwise compromised in an aircraft accident. Physical damage to the batteries themselves can also cause fire. I'm not sure that the hazards associated with electric-powered flight are fully understood at this point in time. I can say for certain, however, that those hazards are not fully understood by me.
Hopefully, there will be other posters on this thread who have a more complete understanding of the hazards associated with electric-powered flight.