Is there a way to see which Power Berries I've found?
Are you talking about keeping track of which ones you've already found or knowing how many you currently have? I believe your onscreen energy gauge updates with each berry you find. As to figuring which particular berries you have found, I don't think there is any way to know other than keeping track yourself with something like Cher's guide or keeping notes. At least it's easier to check than the Goddess or Kappa gems, lol.