If I finished my return i clicked no i don't use direct deposit or my details haven't changed. will i get a personal cheque? or my old DP details from last year?

If you have direct deposit already set up with CRA, your refund will be deposited to that account (If you receive the GST/HST benefit quarterly, it's the same account.).

If you are a CRA My Account holder, you can check your direct deposit details online by signing into your CRA My Account.