The channel coupling effects of internal degrees of freedom like deformations of the interacting nuclei and vibrations have been accounted very well in fusion reactions. The neutron transfer channels with positive Q-values have resulted in the enhancement in the sub-barrier fusion cross-sections in various systems. However, there are few cases in which such effects are not observed, thus, remaining an open question for discussion and further studies. In this respect, the fusion cross-sections of the various combination of projectile - targets have been calculated and compared with experimental data using the coupled channel approach by employing CCFULL and ECC codes. Fusion excitation functions were calculated for \(^{\varvec{30}}\) Si + \(^{\varvec{58,62,64}}\) Ni and \(^{\varvec{32,34,36}}\) S + \(^{\varvec{58,64}}\) Ni systems using two different approaches to unravel the effect of different collective excitations and neutron transfer channels on the sub-barrier fusion cross-sections. Inclusion of coupling to the inelastic excitations in the calculations for \(^{\varvec{30}}\) Si + \(^{\varvec{62,64}}\) Ni, \(^{\varvec{32}}\) S + \(^{\varvec{58}}\) Ni and \(^{\varvec{36}}\) S + \(^{\varvec{64}}\) Ni systems explained the experimental data. The coupling to the transfer channels with positive Q-values along with the inelastic channels was incorporated in calculations and showed a significant influence on fusion cross-sections in \(^{\varvec{32,34}}\) S + \(^{\varvec{64}}\) Ni and \(^{\varvec{34,36}}\) S + \(^{\varvec{58}}\) Ni systems. Upon investigating the role of the two-neutron transfer channels (pick-up and stripping), it was concluded that in the case of \(^{\varvec{30}}\) Si, \(^{\varvec{34}}\) S, \(^{\varvec{36}}\) S + \(^{\varvec{58}}\) Ni systems, the coupling to the two-neutron stripping channel with positive Q-value showed a weak channel coupling effect in the sub-barrier region. For \(^{\varvec{32,34}}\) S + \(^{\varvec{64}}\) Ni systems, a two-neutron pick-up channel with positive Q-value showed a strong influence on the fusion cross-sections.
