Generally, the Art. 210 requirements for branch circuits are prerequisites for applying requirements found elsewhere. This fact is exemplified by the overcurrent protection requirements [Sec. 210.20]. These focus on characterizing and calculating the load, something you must do before sizing the overcurrent protection devices (OCPDs) and conductors.
A continuous load is one that can be expected to operate three hours or more [Art. 100]. Lighting (for example) is a continuous load, u