I don’t currently live in the area, but I always have used FFS plans that are nationwide. I used to drive through MD briefly everyday between home & work. I like FFS because you can go to any doctor you want but pay a little more for out of network providers. You may want to check with the doctors you want to keep and see what insurances they accept.
I believe any Federal Employee can use Blue Cross(BCBS)/Blue or MHBP (despite the name); some like Compass & Foreign Service (FSBP) are limited to certain agencies. I’m just changed from BCBS to FSBP as I know someone that has it and loves it and BCBS is really expensive for the family option. OPM has a pretty good comparison tool https://www.opm.gov/healthcare-insurance/healthcare/plan-information/compare-plans/