Rambam lists confession as an aspect of t'shuva (Yad, T'shuva chapter 2) and possibly of independent value (chapter 1). He notes that t'shuva is insufficient for interpersonal sins and one must appease the wronged person (end of chapter 2) — but that doesn't mean it's unnecessary! (Note also that Rambam's wording "neither t'shuva nor Yom Kipur atone, except for sins between man and God…; interpersonal sins… are not forgiven for him, ever, until he gives his fellow what he owes him and appeases him" makes it sound (to me) like t'shuva is done first.) So it is safe IMO to assume one says the standard confession.
(This is irrespective of any consideration about whom the confession is describing. (It's in the plural.))