  We report on the spectroscopic confirmation of 68 new bright ($G=13.5-17.2$
mag) and blue (pre-)white dwarfs (WDs). This finding has allowed us to almost
double the number of the hottest ($T_{\mathrm{eff}} \geq 60$kK) known WDs
brighter than $G=16$ mag. We increased the number of known ultra-high
excitation (UHE) WDs by 20%, found one unambiguous close binary system
consisting of one DA WD with an irradiated low-mass companion, one DAO, and one
DOA WD that are likely in their transformation phase of becoming pure DA WDs,
one rare, naked O(H) star, two DA and two DAO WDs with $T_{\mathrm{eff}}$
possibly in excess of 100kK, three new DOZ WDs, and three of our targets are
central stars of (possible) planetary nebulae.
  Using non-local thermodynamic equilibrium models, we derived the atmospheric
parameters of these stars and by fitting their spectral energy distribution we
derived their radii, luminosities, and gravity masses. In addition, we derived
their masses in the Kiel and Hertzsprung-Russell diagram (HRD). We find that
Kiel, HRD, and gravity mass agree only in half of the cases. This is not
unexpected and we attribute this to the neglect of metal opacities, possibly
stratified atmospheres, as well as possible uncertainties of the parallax zero
point determination.
  Furthermore, we carried out a search for photometric variability in our
targets using archival data, finding that 26% of our targets are variable. This
includes 15 new variable stars, with only one of them being clearly an
irradiation effect system. Strikingly, the majority of the variable stars
exhibit non-sinusoidal light-curve shapes, which are unlikely explained in
terms of close binary systems. We propose that a significant fraction of all
(not just UHE) WDs develop spots when entering the WD cooling phase. We suggest
that this could be related to the on-set of weak magnetic fields and possibly
diffusion.
