Bit outdated. First paragraph, Westjet (WS) has introduced for more than a few years now a Premium Economy product which is more like domestic First on U.S. airlines. Note that it's not on all a/c and you may be subbed a ex-Sunwing a/c which has no PE cabin at all with no compensation.
2nd paragraph. WestJet is in the process of making the cheap seats more insufferable. There'll be PE (not a bad deal if you book early enough _and_ they don't sub out your booked a/c with one that has none), some E+ product for the first 3-5 rows behind PE with some enhanced catering service and extra pitch, and then reduced pitch (28.5") for everyone else. This is substantially less than AC Rouge.
If you book WS, try to book through DL (codeshares offered). You may be able to cancel/reschedule if your PE flight is subbed out. Also, DL mileage flights can be very cheap (booked LAX-YVR-YYJ for ~12,000 DL miles + $5.6 in taxes).