All of your data—your characters, gear, progress, etc.—are permanently tied to the platform account they were created on. Enabling Cross Save allows you to choose the one data set you want to be able to access across all linked platforms, but this is not an actual transfer of data. If Cross Save is disabled and you put the gear from your Xbox characters in your vault and then start new characters on PC, nothing would be accessible between the two. Your gear would still only be available on Xbox and your new PC characters would have nothing. If you enable Cross Save again and choose Xbox as your active data set, then your Xbox characters and gear would be available on PC for as long as you keep Cross Save enabled. You would not want to choose PC as your active set as that would make your Xbox data inaccessible, and you should not delete your Xbox characters if that's the data you want to access on PC.