Sorry to bump, but i can answer :
The "King's house musketeers" ("mousquetaires de la maison du roi") are Elite often used as Shock troops, and they used horses for moving. They had no equivalent in this era.
Normal musketeers are, well, normal troops.
Just use the normal as standard french troop, and use the King's as Elite : 2 moves, better attack (shock troop), better defense (they are the royal guard). Maybe given by a wonder ?