If you apply for the OWP and the inland PR application together, in the same envelope, then they will process the OWP automatically as soon as they grant AIP. That means you will get the OWP sooner than if you wait for the AIP letter to arrive, then apply for the OWP.
OWP does not mean you can leave Canada safely. You still have to satisfy the IO that you are a genuine temporary resident when returning, and while they are supposed to facilitate re-entry in that situation, they know you plan to live in Canada permanently and have strong ties, so if they have any doubts you would leave if refused, they could deny you entry. With an outland app that wouldn't matter, but with an inland app that would eventually result in the app being refused simply because you are no longer in Canada, and being in Canada is a requirement of that application class.
It's a personal decision, but not one that should be taken lightly. If the need to leave Canada is sufficient that you would be willing to start the PR application process again, then by all means, but I wouldn't recommend leaving without a really good reason - there is a risk involved.