\usepackage[font=small]{subcaption}
\DeclareCaptionLabelSeparator{septoptesi}{.\quad}
\captionsetup{labelsep=septoptesi, figureposition=bottom, font=small}
\captionsetup[table]{position=above}
\renewcommand\thesubfigure{(\alph{subfigure})}
\captionsetup[subfigure]{labelformat=simple}