I don't have access to the Atlas layout design you refereed to so I don't want to comment on the specifics of the layout or if it would require a PM42.
I do know this from experience. You can wire and Run your layout with the Zephyr. Wiring provision for a future PM42 might be advised. If you can Post a copy of your layout to the Group may make things easier.
Placement of the plastic insulation joiners is critical. Now is the time to decide what you want to do with your layout in the future, and install your buss wiring accordingly. Take into consideration if you want to create blocks, and possibly future automated signaling, operating crossing gates etc. Trying to create blocks at a later date can be more difficult.