I always thought that the many plurals in the amida refer to the Jewish people.
But the wording of the besefer chaim addition to the sim shalom paragraph of the amida for this time of year (yamim noraim) seems not to fit with that. The addition says, "we and all your people, the house of Israel". This seems to imply that the plurals of the amida (e.g., modim anachnu lach) refers to a smaller group, presumably the kahal.
Have authorities opined on this and if so, what do they say?