I have a recipe that calls for "poaching" octopus in red wine vinegar before a three-day marinade in another solution. I don't have that much red wine vinegar, but I've got many vinegars ranging from distilled white to white champagne to rice wine, etc. (Also have lots of balsamic but assume that's not really a mixer.)
I think vinegars vary by acid level. Any ideas about what it means to mix them for such a purpose?