A few recommendations are Open City, Tryst, Pitango, and Coupe – one theme here is that the Tryst family of locations all prioritize a wide array of seating. There does tend to be an inverse relationship between the number of seats and the quality of coffee, but I don't think that's particular to DC. Some hit-or-miss spots seating-wise are the two Emissary locations and TCB, both serve good coffee but are in high demand.