First I'd like to state the obvious: Christopher Guest is the king of this genre.
Other dynamics in mockumentaries are hard working people -
Kenny and
The Big Tease - and love outside of Hollywood -
Confetti,
The Office US & UK.
Two missing from the list are
Sweet and Lowdown and
District 9.
I find the films I like the most in this genre stay rigidly within the documentary format. Cheating of any kind quickly peels back the format and reveals the cheap gimmick underneath.