What type of electric heating system is the most energy efficient?
100% of electricity is converted to energy is true. But what is the energy used for? Generate heat, as in resistive heating? All of the electricity is converted to heat, sounds efficient. But you can do better. You can use your electric energy to move heat obtained for free from somewhere else. In other words, a heat pump is more efficient than resistive heat. The source of free heat can be the air, the ground, or even ground water. How the heat that is moved into your house is distributed can vary. You can blow heated air around, or you can move heated fluid around. The heated fluid can give up its heat at radiators, or base board heaters, or into your floor.

There's many options, but you should get heat by moving it rather than causing resistive wires to give it up.