  Gauge theories with gauge group $SU(N)$ and quarks belonging to arbitrary
representations of $SU(N)$ form a rich landscape of QCD-like theories, whose
study can shed new light on the properties of confinement. Four cases are
particularly worth of interest: quarks in the fundamental representation,
quarks in the 2-indice (anti)symmetric representation and quarks in the adjoint
representation. The last three corresponding QCD-like theories are equivalent
at large-$N$ for bosonic observables: It is the orientifold equivalence. The
behavior of the lightest vector meson mass versus $N$ has been studied in
quenched lattice QCD in the chiral limit in these theories. We show that the
observed behaviors are compatible with a string tension proportional to the
quadratic Casimir of $SU(N)$ in the quark color representation, $\textit{i.e.}$
with the Casimir scaling hypothesis. The large-$N$ limit of some excited meson
masses computed in quenched lattice QCD with quarks in the fundamental
representation is also shown to be compatible with QCD string's well-known
signature: Regge trajectories.
