  While classic quantum chaos originated from the idea to set into context
nonlinear physics and Hermitian quantum mechanics, non-Hermitian models have
enhanced the field in recent years. At the same time, low-dimensional effective
matrix models have proven to be a powerful tool in accessing the physical
properties of a system in a semiquantitative manner. Here, we focus on two
realizations of non-Hermitian physics in mesoscopic systems. First, we consider
spiral optical microcavities in which the asymmetric scattering between
whispering gallery modes induces the non-Hermitian behaviour. Second, for
parity-time (PT) symmetric ladder lattices we compare circular and M\"obius
geometries. We find the effective coupling between even and odd parity modes to
be symmetric but complex in a microscopically derived 2 x 2 matrix model,
resulting in non-Hermitian behaviour as well. Most importantly, the M\"obius
topology acts like a scatterer that induces a qualitatively new form of
(avoided) level crossing - a PT-broken phase terminated by exceptional points -
resulting from the symmetric but non-Hermitian coupling.
