Russian people are very different one from the other.

Or:

Russian people vary greatly.

If you say, "Russian people are very different," that means that Russians are different from other nationalities, e.g. Americans, Chinese, South Africans, etc.  But that could still mean that all Russians are the same.

If you say "Russian people are very different one from the other" or "Russian people vary greatly," it means that there are different kinds of Russian people.  And that is one of the main points of your post.

People in Saint Peterburg.

Russian people are very different. Since our country is big enough you can meet different types of people. I live in the north of my country in Saint-Peterburg. It seems to me that geography has lead to some specific tempermental attributes of my city's people. Usually, we have only 70 sunny days a year. And I think it's one of the main reasons for the glum faces you can see walking around the city. I wish our weather was like some other warm country like Brasil or Australia for example. It would be splendid. Saint Peterburg is like Winterfell of Game of Thrones. :)