  In this work, we study the properties of neutron stars using the linear
Relativistic Mean-Field (RMF) theory and consider multiple degrees of freedom
inside neutron stars, including hyperons and $\Delta$ resonances. We
investigate different coupling parameters $x_{\sigma \Delta}$ between $\Delta$
resonances and nucleons and compare the differences between neutron stars with
and without strange mesons $\sigma^*$ and $\phi$. These effects include
particle number distributions, equations of state (EOS), mass-radius relations,
and tidal deformabilities. To overcome the "hyperon puzzle," we employ the
$\sigma-cut$ scheme to obtain neutron stars with masses up to $2M_{\odot}$. We
find that strange mesons appear at around 3$\rho_0$ and reduce the critical
density of baryons in the high-density region. With increasing coupling
parameter $x_{\sigma \Delta}$, the $\Delta$ resonances suppress hyperons,
leading to a shift of the critical density towards lower values. The early
appearance of $\Delta$ resonances may play a crucial role in the stability of
neutron stars. Strange mesons soften the EOS slightly, while $\Delta$
resonances predominantly soften the EOS in the low-density region. By
calculating tidal deformabilities and comparing with astronomical observation
GW170817, we find that the inclusion of $\Delta$ resonances decreases the
radius of neutron stars.
