Did Napoleon bring the French Francs over, or did the (many) local currencies remain in use? I understood that the area's tolls on the river were unified, but have a hard time imagining how exactly that happened
There is a book on the subject of the Rhineland subjugation called "From Reich to State: The Rhineland in the Revolutionary Age, 1780-1830" by Michael Rowe. On p. 203 of this book it says that many currencies, including the Franc, continued to be used. The main impact of the takeover was that the Franc became the only currency in which taxes could be paid, therefore the Franc increased in importance. Nevertheless, the region still continued to use a potpourri of different kinds of money.