As long as neither the OWP application, nor the Inland application package, does not have any errors on your part (meaning either/both are returned to you) and you pay the correct amount ($255, NOT $155), the approval will be automatic, since the only requirement it that you have submitted an Inland application and CIC has received it.
If the Inland application is returned, after you submit an OWP, you risk losing Implied Status (unless you re-submit the Inland application before your true legal status expires).