The actual model designation for all CRJs is a CL600-2B19. The difference between a 100 and 200 is the engine. The Type Certificate contains this note:
The RJ200 is a marketing designation for the Regional Jet Series 100 aircraft
with the General Electric CF-34-3B1 engines installed and is identified as
RJ100 in this TCDS. All Airworthiness Directives issued against any 100
Series aircraft are similarly applicable to the 200 Series.
So as far as certification and model numbers go, There is no real difference between the 100 and 200 and beyond marketing, there's no such thing.
The series "440" version, has a maximum seating capacity of 44 pax versus the 50 pax of the "100" series.
Bombardier has the following information on their website with respect to the other model designations:
Bombardier Aerospace currently offers three versions of the CRJ200. The standard Bombardier CRJ200 has a maximum take-off weight of 47,450 pounds (21,523 kg) and a range of 987 nm (1,825 km). The Extended Range (ER) variant has a maximum take-off weight of 51,000 pounds (23,134 kg) and range of 1,645 nm (3,045 km). The Long Range (LR) model has a maximum take-off weight of 53,000 pounds (24,041 kg) and a range of 2,005 nm (3,713 km).
There's also an "SE" version that is offered as a business aircraft.