A detailed study of top-quark polarizations and $t \bar t$ charge asymmetries, induced by stop-pair production at the LHC and the subsequent decays $\tilde t_1 \to t \tilde \chi_1^0$, is performed within the effective description of squarks interactions, which includes the effective Yukawa couplings and another logarithmic term encoding the supersymmetry breaking. This effective approach is more suitable for their introduction in Monte-Carlo simulations and we make use of its implementation in {\tt MadGraph} in order to investigate the possibilities of the charge asymmetry $A_\text{C}$, measured at the LHC and consistent with the SM expectations, to discriminate among different SUSY scenarios and analyze the implications of these scenarios on the top polarizations and related observables.