Who is the best candidate for a couples dating?

If you and your partner are on the same page, and both of you make up your minds to have a couples dating, who is the best candidate for a couple date? Are you prefer to invite someone you are familiar to? Or you are willing to find a totally stranger on a tinder for threesomes dating site? Actually, if the third partner is your friend and you can feel safer and be more open during the date. If the person is a stranger, you don't need to worry what if the date ends bad. Because you don't have to see this guy after date.