  A joint fit of the mass and redshift distributions of the population of
Binary Black Holes detected with Gravitational-Wave observations can be used to
obtain constraints on the Hubble parameter and on deviations from General
Relativity in the propagation of Gravitational Waves. We first present
applications of this technique to the latest catalog of Gravitational-Wave
events, focusing on the comparison of different parametrizations for the
source-frame mass distribution of Black Hole Binaries. We find that models with
more than one feature are favourite by the data, as suggested by population
studies, even when varying the cosmology. Then, we discuss perspectives for the
use of this technique with third generation Gravitational-Wave detectors,
exploiting the recently developed Fisher information matrix Python code GWFAST.
