Lots to unpack here....
G-line seniority (line holder) is about 600 numbers more senior on the bus than guppy regardless of most junior; that’s a better indicator of how long you’d be on reserve. Do you live (or plan to) local to one of the bases? Dulles is by far the majority of flying, but bus does higher percentage of DCA trips than guppy. BWI 737 trips are largely non-commutable unless you live in a SWA hub, but lots of MD peeps bid those.
Everyone in my class who bid an aircraft in an attempt to have better seniority at their desired base was wrong within a year. Caveat emptor. If you’re wrong, you can swap in two years.