To anyone who is reading this thread as they're looking to travelling with PR application in progress (or about to start).
Inland applicant must stay with your sponsor throughout the process, not only inside Canada but with your sponsor. You might have a short trip to US as they won't check for visa upon returning. But travel to anywhere else that need a visa for return might risk your PR application if they deny your entry for any reason. It's only a risk but you're the one to decide to take the risk or not.
However, if you're living with your sponsor in Canada but you want/plan to travel after submitting your application, you can opt for Outland option. In this case your application will be processed outside of Canada. The only downside of that is if they need an interview you will have to travel to the assigned visa office which usually is in your home country.