Yeah, gearboxes capable of redistributing engine power were really not a thing in the early days. One propeller per engine was the way it was done.
The dual paddle wheels of a side-paddle steamer were typically connected by a solid shaft that did not allow for independent use of the paddles, although some designs had clutches to allow for semi-independent paddling for greater maneuverability.
(Amusingly, it was found that clutched paddlewheels could not be safely used on passenger steamers because when a ship came into port, the passengers would rush to the dock side of the ship. This meant that the ship was habitually imbalanced as it maneuvered to dock, and differential paddling was just too dangerous to use when so imbalanced.)