-yes,ducted fan is another type of propeller(generator of thrust force),but both are working on the equal phisical principes...We're talking about different things - open prop vs ducted fan.
-ducted fan inside of the fuselage have small diameter
=low specific thrust (big specific power/thrust/surface !)
conterrotating fans can help with this problem...
see todays turbofans (conter rotating too).