Bounded equidistribution of special subvarieties II

In this paper, we prove a lower bound for the Galois orbits of a pure special subvariety in a general mixed Shimura variety. For special subvarieties that are not pure, we propose the notion of test invariants as a substitute for the lower bound estimation, and prove the bounded equidistribution for sequences of special subvarieties with uniformly bounded test invariants in a given mixed Shimura variety. Both the estimation and the bounded equidistribution rely on the Generalized Riemann Hypothesis for CM fields, similar to the pure case treated by E. Ullmo and A. Yafaev as part of the ergodic-Galois alternative for the Andr\'e-Oort conjecture for pure Shimura varieties.