  We consider (effective) Quantum General Relativity coupled to the Standard
Model and study its transversality. To this end, we provide all propagator and
three-valent vertex Feynman rules. Then we examine the longitudinal, identical
and transversal projection tensors for the de Donder gauge fixing and the
Lorenz gauge fixing. In particular, we recall several identities from Quantum
Yang--Mills theory and introduce their counterparts in (effective) Quantum
General Relativity: This includes decompositions of the longitudinal projection
tensors as well as expressions of the corresponding propagators in terms of
their transversal structure, together with longitudinal contraction identities
for all three-valent vertex Feynman rules. In addition, we introduce the notion
of an optimal gauge fixing as the natural choice for a given gauge theory: In
particular, we find that this is the de Donder gauge fixing in General
Relativity and the Lorenz gauge fixing in Yang--Mills theory.
