I have the Whirlpool Corporation Gladiator shelves like that & I believe the Costco & Wallyworld products are thinner-gauge. Compare the load rating, the Gladiator is 2000 lbs equally-distributed per shelf for the long unit, they also come in shorter lengths, too to fit your space.
i narrowed the depth to 13" to fit the space on the side of my garage door return, I needed to be able to store my record collection (2000+) along the wall in that narrow space. I used a combination of aluminium square stock and PT square wood stock ripped to size, and 1/4" hex machine screws & flat washers to bolt together the shortened steel end framing, and the individual shelf supports that help hold the load in the middle of the wire shelving. Depending on the length of the shelf, there may be either two or three of those "clip-in" reinforcements per shelf.
The shallower shelves fit neatly into my limited side wall return space, and allov me to park my GMC truck in the garage if I need to, and still be able to exit the truck.
I thought of putting masonite on the wire shelf surface, but the load there is pretty much permanent. If you were going to be placing & removing things frequently in the shelf, then a solid surface on top of the wire rack, instead of the bare wire rack might work for you.
If you put a mezzanine or loft above the shelves, these are a good height.
A tip, I put the first shelf maybe 6" above grade so I can slip under the shelf things like floor jacks, cherry pickers, spare lolly columns, etc, and it also makes it easier to keep clean, or to retrieve something that falls to the floor. I usually use a handheld blower to 'sweep' under the shelves every couple of weeks.
