All you have to do is sign out of icloud, and make sure that your game centre is also turned off. Then, open the app with the new Apple ID you made, and voila!, it should sync. Tell me how it goes, and, will it have everything up to date with 15.7? Just curious, hope this helps.
Edit: sorry, you said personal info? Do you mean friends, clans etc? Because from my memory, they will be saved, so maybe after syncing your new account, tell your clan you have to temporarily leave, copy your friends ids (I know, it’s quite an annoying process), and copy all other info, then leave the clan, delete friends and anything else you need, and then post the account.
This being said, you probably won’t need to re-enter your friends list or anything when logging back into your old account, but if you are logging in through iCloud via the same device you used to make the hack, it will be stored on local and you probably will have to re enter the list. If you are jail broken (which, on a side note, I know not much about), you could clear local data, but this will remove all your coins/gems/other currencies, but nothing else to my knowledge. I advise you use, if possible, a different device to make the hack, then sync that to the new iCloud account, so none of your personal data gets lost. Also, coins and other currencies will not sync onto the iCloud account, so beware that.