yes everything needs to be rated for 24v.
"Is the benefit of the 24v system faster heat times?"
This depends on your bed, standard 12/24v PCB type beds are the same wattage at 12 or 24v, so heats up the same. Those that experience faster heat up normally have under powered 12v supplies or to thin wires to the heated bed.
It does mean you have more power, so you can have higher wattage beds
Steppers, they move faster and have more holding torque with higher voltages.
With higher voltage and lower currents thinner wires can be used.
Some have reported that some stepper drivers are nosier with higher voltages.