When it comes to electric space heaters, if they have the proper protective elements (Such as a thermal fuse and a tip over switch) all are equally safe/dangerous. Also all produce the exact same amount of heat per watt.
The O/P also ask "if plugged in does the heat also burn propane" (or use propane)
The RV's built in furnace is a propane furnace, So yes, it eats propane.
Very little electricity (just the fan, control and DSI power)
but the heat is from burning propane.
The furnace in an RV runs on 12 volt and propane.