LM2596s-Adj dc to dc buck converter
Yes, the diode voltage drop \$V_f\$ in a buck appears in the input-to-output transfer function \$\frac{V_{out}}{V_{in}}\$ weighted by \$(1-D)\$, \$D\$ being the duty ratio. So if the \$V_f\$ is too big, you will see a drop in the output but the loop should compensate by an increase of the duty ratio. Nevertheless, efficiency will drop as \$V_f\$ grows especially in CCM when \$V_{out}\$ is much smaller than \$V_{in}\$. As the diode voltage drop at a given current is directly related to its die size, a higher current rating type will imply a lower \$V_f\$.