Capital Airport, Daxing, the central historic districts, CBD, embassy area and rail stations create different gateways to the city. A visit becomes easier when it begins with the practical question of where the traveller needs to be first and what state they need to arrive in.
The best plan is not the fullest one. It is the one that leaves sufficient time around a fixed appointment or visit, while preserving an evening, meal or quieter interval that gives the city its own character.