  The IACOB and OWN surveys are two ambitious complementary observational
projects which have made available a large multi-epoch spectroscopic database
of optical high resolution spectra of Galactic massive O-type stars. As a first
step in the study of the full sample of (more than 350) O stars surveyed by the
IACOB/OWN projects, we have performed the quantitative spectroscopic analysis
of a subsample of 128 stars included in the modern grid of O-type standards for
spectral classification. We use semi-automatized tools to determine the set of
spectroscopic parameters that can be obtained from the optical spectrum of
O-type stars. We also benefit from the multi-epoch character of the surveys to
perform a spectroscopic variability study of the sample, accounting for
spectroscopic binarity and variability of the main wind diagnostic lines. We
provide a general overview of the stellar and wind parameters of this reference
sample, and updated recipes for the SpT\,--\,Teff/log g calibrations for
Galactic O-type stars. We evaluate our semi-automatized analysis strategy with
$\sim$40 stars from the literature, and find a good agreement. The agreement
between the synthetic spectra associated with fastwind best fitting models and
the observed spectra is good for most targets, but 46 stars present a
particular behavior of the wind diagnostic lines that cannot be reproduced by
our grid of spherically symmetric unclumped models. These are potential targets
of interest for more detailed investigations of clumpy winds and/or the
existence of additional circumstellar components. Last, our variability study
has led to the detection of signatures of spectroscopic binarity in 27\% of the
stars and small amplitude radial velocity variations in the photospheric lines
of another 30\%. Additionally, 31\% of the investigated stars show variability
in the wind diagnostic lines.
