I composed my initial Answer based on how the Q was initially posted, as it has been revised this will feature a blend of quotes from the original and the current wording..... because I CBA to completely rewrite ^_^
If I don't have any plywood available, what should I factors should I consider when selecting other wood to make my cleats from?
This embodies ...
I'll take a stab at the question in your comment:
"how do I size and select wood for making French Cleats
As used in home settings (kitchens, laundry rooms, pantries, garages, shops), French cleats are typically used to support cabinets and their contents. In my experience, it's common for cleats to be attached to the wall to facilitate hanging ...
For larger loads, try to find hardwood. Maybe something like cherry which resists checking and cracking. With any wood, use a minimum of one half inch thickness, preferably three quarters inch. A plain strip at the lower end of the cabinet, etc, helps to keep the unit plumb.
Generally speaking, the exterior doors to your house are (or, at least, can be made) reasonably air tight. You'll want to use similar type seals for your door.
I'm thinking a product similar to this self adhesive gasket:
Image of M-D 20-ft x 1/2-in Black Door Seal Silicone Door Weatherstrip supplied by Lowes.com. No endorsement of product or vendor intended ...