Higher voltage will give you higher power or output to the load.

I don't have a disagreement with a brushed motor, it will speed up. A 3 phase DC motor may or may not depending upon the ECS - usually it will also speed up.

However an ignition circuit depending upon how its designed it may or may not provide a hotter spark. If the ignition uses a switching designed boost source for the coil the output will tend to be self stabilized. Ask Bcchi what his does.

John