Inland means you can't leave until the process is completed. Some people, who come from visa-exempt countries, have left and re-entered successfully but there is no guarantee of re-entry. You require a visa, you should not leave. If you are refused re-entry, you will have to start your application over again.
I am wondering why, if you just received an OWP, you want to leave? Most people eagerly await their OWP so they can work! If you don't have a job to come back to, you likely wouldn't be allowed back in to Canada. And refer to reasons above....
Since you have been sent a letter stating a decision has been made and medicals received, it sounds like you have completed the process and will soon be contacted for a landing interview. Depending on your local office, a landing interview will happen in the next couple of months. Upon landing, a PR card will be required to travel, unless you apply and are approved for a travel document for emergency travel. PR cards are taking anywhere from 30-70 working days to arrive right now.