What kind of document was the constitution in the summer of 1787? what does this fact indicate about the power of "we the people"?

The constitution was the declaration of independence.

We the People” includes all the citizens of the Untied States of America. This phrase is shows that it was just the framers of the Constitution of the legislators that have powers to the government. 

Without the people lending the power there would not have been able to become constitute guideline for the Republican