  Spontaneous Hall conductivity has recently been reported in the triangular
lattice antiferromagnet Co$_{1/3}$TaS$_2$ under a zero magnetic field. This
phenomenon originates from the distinctive noncoplanar triple-Q magnetic ground
state, possessing uniform real-space Berry curvature characterized by scalar
spin chirality. We investigated the physical properties of Co$_{1/3}$TaS$_2$ by
judiciously controlling the composition, revealing a drastic change in its bulk
properties, even by slight variations in cobalt composition, despite the same
crystal structure. For $0.299 < x < 0.325$, Co$_x$TaS$_2$ keeps all the
characteristics of the ground state consistent with the previous studies -- two
antiferromagnetic phase transitions at $T_{N1}$ and $T_{N2} (< T_{N1})$, a
large spontaneous Hall conductivity (${\sigma}_{xy} (H=0)$), and a weak
ferromagnetic moment along the c-axis. However, samples with $x > 0.330$
exhibit distinct bulk properties, including the absence of both ${\sigma}_{xy}
(H=0)$ and the weak ferromagnetic moment. Our neutron diffraction data reveal
that Co$_x$TaS$_2$ with $x > 0.330$ develops coplanar helical magnetic order
with $q_{m1} = (1/3, 0, 0)$. This is entirely different from what has been seen
in $x < 0.325$, explaining the observed composition dependence.
