The "key" to this is that, in order to benefit from "implied status", the inland PR application and the extension application (with the Work Permit option checked as a change of condition, plus the $150 fee paid) has to be received by CPC-Vegreville before her current status expires. What usually trips up US applicants is that they often are admitted to Canada without being documented - so unless you can prove the date your wife entered the country (with a Visitor Record or a passport stamp), I highly recommend that you NOT apply inland. You'd be setting yourselves up to have the application delayed by transfer to a local office for processing before they give first stage approval and that can get her "stuck" in Canada without status (or the ability to work) for years!
That said, why would you submit inland and wait (even for a straight-forward ap) 9-10 months just to get an open work permit when Buffalo is currently finalizing spousal aps in as little as 6 months (and then she'd be able to work anyway immediately after landing)? I know Buffalo's posted timeline is 11 months, but I've seen - just this past week - three or four spousal aps finalized within 6 months of receipt by Buffalo. I know you say you know the pros and cons but it honestly doesn't make sense unless you're under some preconceived notion that she has to do this to stay with you while waiting for her PR to finalize. Or that the OWP will come sooner than the PR request from Buffalo (not likely). Apply inland and you're 12-18 months (at best) waiting for finalization and you lose the right of appeal. You can apply outland and still apply to extend her status as a visitor while she waits. Your call, of course, but please make sure you know why your reasons for applying inland are sound - and, basically, unless someone is already in Canada with a work permit and wanting to preserve their right to continue to work (or go to school if it's a study permit), the general consensus is that inland is not the way to go - especially for US citizen applicants. In the four plus years I've been around here, there's only been one US person who didn't regret applying inland. Good Luck.