A neat job, and what follows is not meant to be critical, but rather to illustrate how codes can vary by region, if not by municipality. My plumbing background is in the Los Angeles area. I've been away a few years, but I think what I am going to say still holds. First of all, the wall between the garage and house is required to be fire rated and cannot be penetrated by plastic. That means the WM box has to be metal and the clean-out cast iron (or copper) with a brass plug. That mechanical vent, that goes - VTR only. Also the PEX is out, it would have to be copper or galvanized. Both ways will operate fine, but that installation in the burbs of LA gets turned down on multiple counts. I just find that interesting.