In late 19th century and Napoleonic time - one did realize the waste of ammunition of unaimed mass fire.
As consequence - it became less important to fire quickly, and more important to hit.
As for the rifle versus musket, on a mass target, like a battlion in close order there would be almost no differences if a rifleman had a musket or a rifle.
With a musket he could not hit as accurate - but balance this out with quicker and still aimed shoots.
He had to be in skirmish order to be able to do this.
Scharnhorst took some tests on this and verified it to a larger or lesser extend.
The difference would be single targets - like enemy skirmishers, using terrain to hide themselves and seek cover.
Here a rifleman could hit much more accurate while he himself would be very difficult to hit at a distance of 300 paces when the adversary was armed with a smoothbore musket.
So - how would the French voltigeurs cope - fighting against a unit which was armed with rifles and specialists in hitting, as well as all other aspects of the small war?
The couldn't cope with it, as one eye witness clearly states, or what the experience in the Peninsular would proove. The British skirmish line would be impregnable for the French tirailleurs and they could not wear down the line infantry.
This was not achieved by riflemen alone but by the combination of light infantry with smoothbore muskets AND light infantry with rifles.