Hi
Below is a good link and should cover most of the questions you have.
http://www.napolun.com/mirror/web2.airmail.net/napoleon/Prussian_infantry.htm
Fusiliers were basically Light Infantry and 1813 onwards there would usually be three battalions brigades together, 1 Fusilier and 2 Musketeer (or Line) Battalions.
The Fusiliers usually had a plume and some level of training in Light Infantry tactics, they were armed with muskets, only Jagers had Rifles.
Good luck with your new Prussian Army