The three majors have an area:
BWI and the surrounding area is Chesapeake (CHP)
IAD is the Shenandoah area (SHD)
DCA is the Mount Vernon area(MTV)
And then there’s James River… (JRV) which is RIC. In their defense they work a lot of satellite traffic though ?
MTV CHP and SHD work their own arrivals and departures but the airspace is so layered that some areas work each other’s stuff. For example, CHP and SHD feed departures to MTV to be blended with theirs and fed to the center.
SHD has a lot of capped airspace because arrivals to CHP and MTV go over the top.
It’s not the traffic that will get you but the airspace, procedures and congestion.
the special flight rules airspace (SFRA) is another complicated procedure you won’t really see anywhere else.