Ok so you should apply right away !
Applying for an OWP with the Inland PR application will give your spouse "implied status", so he will not have to extend his visitor visa.
So, go to IRCC website again and look for OWP for spouse or common law partners in Canada: use the search bar or go to the PR application section and go from there.
Check the documents and check the fees as there are 2 different fees to pay for the OWP.
Do it thoroughly, don't miss any documents or fees, as if it gets returned, then he loses the implied status advantage and will have to extend the visitors visa.
The OWP gets to you in an average of 3 months if everything is ok.
When you send it together with PR is on paper, but check because I think you can apply online.
Hope it hoes smooth