\documentclass{article}
\usepackage{xsim,lipsum}

\NewDocumentCommand\printcompletepoints{}{%
  \TotalExerciseGoals{points + bonus-points}
    {\,\XSIMtranslate{point}}
    {\,\XSIMtranslate{points}}%
}

\NewDocumentCommand\pointsandbonus{}{%
  \TotalExerciseGoal{points}{}{}%
  \IfExerciseGoalsSumTF{bonus-points}{=0}
    {}
    {\,(+\,\TotalExerciseGoal{bonus-points}{}{})}%
  \,\XSIMtranslate{points}%
}

\begin{document}

\begin{exercise}[points=3,bonus-points=1]
  \lipsum[4]
\end{exercise}

\begin{exercise}[points=8,bonus-points=3]
  \lipsum[4]
\end{exercise}

\printtotalpoints\ vs.\@ \printcompletepoints\ vs.\@ \pointsandbonus

\end{document}