Is peoples a word?

Yes, it’s the plural of “people”.

But, you say, “people” is the plural of “person”. Well, yes. But also no.
“People” actually has two meanings: one is the plural of “person” and simply means two or more persons. But the other is a singular noun that refers to a group of persons; the group is singular even though it is composed of a plurality of elements.

If you want real fun, parse the difference between “all the people of the world” and “all the peoples of the world”. Both are valid references but to two entirely different collectives.

Legal documents often use “persons” as the plural of “person” to avoid the ambiguity inherent in the word “people”